car speed checker with lcd display quotation

The project is a speed checker system that can detect rash driving and any kind of speed violation on highways and alert the traffic authorities. The conventional system uses a handheld radar gun which is aimed at the vehicle to record its speed and if there is any speed violation, nearest police station is informed. This process involves a lot of time consumption. Hence the proposed system is used to check the speed by calculating the time taken to travel between two set points at certain distance.

An IR transmitter and a receiver are installed on the set points on either side of the road. A control unit calculates the time taken by the vehicle to travel from one set point to other and calculates the speed that is displayed on seven segment display. If the calculated speed limit exceeds the set speed, a buzzer is sound which alerts the road transport authority.

Radar speed signs(also known as driver feedback signs, speed display signs, YOUR SPEED signs, and radar speed displays) are traffic calming devices designed to slow speeders down by alerting them of their speed. They are being used across the country, and around the world, because they are effective at slowing speeding drivers down, making roads safer for everyone.

“Provide people with information about their actions in real time (or something close to it), then give them an opportunity to change those actions, pushing them toward better behaviors. Action, information, reaction.”

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Automated license plate readers (ALPRs) are high-speed, computer-controlled camera systems that are typically mounted on street poles, streetlights, highway overpasses, mobile trailers, or attached to police squad cars. ALPRs automatically capture all license plate numbers that come into view, along with the location, date, and time. The data, which includes photographs of the vehicle and sometimes its driver and passengers, is then uploaded to a central server.

Vendors say that the information collected can be used by police to find out where a plate has been in the past, to determine whether a vehicle was at the scene of a crime, to identify travel patterns, and even to discover vehicles that may be associated with each other. Law enforcement agencies can choose to share their information with thousands of otheragencies.

Drivers have no control over whether their vehicle displays a license plate because the government requires all car, truck, and motorcycle drivers to display license plates in public view. So it’s particularly disturbing that automatic license plate readers are used to track and record the movements of millions of ordinary people, even though the overwhelming majority are not connected to a crime.

These are installed in a fixed location, such as a traffic light, a telephone pole, the entrance of a facility, or a freeway exit ramp. These cameras generally capture only vehicles in motion that pass within view.

If multiple stationary ALPR cameras are installed along a single thoroughfare, the data can reveal what direction and what speed a car is traveling. If the data are stored over time, they can reveal every time a particular plate has passed a given location, allowing the government to infer that the driver likely lives or works close by.

Stationary cameras can sometimes be moved. For example, surveillance vans or truck trailers can be outfitted with ALPR systems and then parked at strategic locations, such as gun shows or political rallies.

ALPR cameras are often used in conjunction with automated red-light and speed enforcement systems, and also as a means of assessing tolls on roads and bridges.

These are often attached to police patrol cars, allowing law enforcement officers to capture data from license plates as they drive around the city throughout their shifts. In most cases, these cameras are turned on at the beginning of a shift and not turned off again until the end of the shift. Also, private vendors like Vigilant Solutions capture plate data with mobile ALPRs and then sell that data to police agencies and others.

In addition to capturing images of passing vehicles, mobile ALPR cameras are effective at capturing license plates of parked cars. For example, a patrol car may drive around a public parking lot capturing hundreds of vehicles’ plates in minutes.

Most of this ALPR data is stored in databases for extended periods of time—often as much as five years. The databases may be maintained by the police departments, but often they are maintained by private companies such as Vigilant Technologies. Law enforcement agencies without their own ALPR systems can access data collected by other law enforcement agencies through regional sharing systems and networks operated by these private companies. Several companies operate independent, non-law enforcement ALPR databases, contracting with drivers to put cameras on private vehicles to collect the information. These data are then sold to companies like insurers, but law enforcement can also purchase access to this commercial data on a subscription basis.

Law enforcement agencies will often pre-load a list of license plates that the ALPR system is actively looking for—such as stolen vehicles and vehicles associated with outstanding warrants. Police officers can also create their own hotlists. If the ALPR camera scans a plate on the list, the system sends an alert to the officer in the squad car (if it"s a mobile reader) or the agency (if it"s a fixed reader). Some hotlists include low-level misdemeanors and traffic offenses. Some agencies use these hotlists to generate revenue by stopping citation scofflaws.

ALPRs collect license plate numbers and location data along with the exact date and time the license plate was encountered. Some systems are able to capture make and model of the vehicle. They can collect thousands of plates per minute. One vendor brags that its dataset includes more than 6.5 billion scans and grows at a rate of 120-million data points each month.

When combined, ALPR data can reveal the direction and speed a person traveled through triangulation. In aggregate over time, the data can reveal a vehicle’s historical travel. With algorithms applied to the data, the systems can reveal regular travel patterns and predict where a driver may be in the future. The data also reveal all visitors to a particular location.

The data generally does not include the driver’s name. However, law enforcement officers can use other databases to connect individual names with their license plate numbers.

ALPR data is gathered indiscriminately, collecting information on millions of ordinary people. By plotting vehicle times and locations and tracing past movements, police can use stored data to paint a very specific portrait of drivers’ lives, determining past patterns of behavior and possibly even predicting future ones—in spite of the fact that the vast majority of people whose license plate data is collected and stored have not even been accused of a crime. Without ALPR technology, law enforcement officers must collect license plates by hand. This creates practical limitations on the amount of data that can be collected and means officers must make choices about which vehicles they are going to track. ALPR technology removes those limitations and allows officers to track everyone, allowing for faster and broader collection of license plates with far reduced staffing requirements.

By adding a license plate to a “hot list,” officers can use ALPR to automatically identify or track particular vehicles in real time. Licenses plates are often added to hot lists because the vehicle is stolen or associated with an outstanding warrant. Officers may also add a plate number to the list if the vehicle has been seen at the scene of a crime, the owner is a suspect in a crime, or the vehicle is believed to be associated with a gang. Hot lists often include low-level offenses, too.

Training materials, policies and laws in some jurisdictions instruct officers that a hot-list alert on its own may not be enough to warrant a stop. Officers are instructed to visually confirm that a plate number is a match. Failure to manually confirm, combined with machine error, has caused wrongful stops.

Law enforcement claims that ALPR data has been used to, for example, recover stolen cars or find abducted children. However, police have also used ALPR data for mass enforcement of less serious offenses, such as searching for uninsured drivers or tracking down individuals with overdue court fees.

The ACLU estimates that less than 0.2 percent of plate scans are linked to criminal activity or vehicle registration issues. Many law enforcement agencies store ALPR data for years, and share it with other law enforcement agencies and federal agencies.

Vigilant Solutions" subsidiary Digital Recognition Network, along with MVTrac, are the two main companies hiring contractors to collect ALPR data across the country. The companies then share the commercially-collected data not just with law enforcement but also with auto recovery (aka "repo") companies, banks, credit reporting agencies, and insurance companies.Data collected by private entities does not have retention limits and is not subject to sunshine laws, or any of the other safeguards that are sometimes found in the government sector.

In addition to deliberate misuse, ALPRs sometimes misread plates, leading to dire consequences. In 2009, San Francisco police pulled over Denise Green, an African-American city worker, handcuffed her at gunpoint, forced her to her knees, and searched both her and her vehicle—all because her car was misidentified as stolen due to a license plate reader error. Her experience led the U.S. Ninth Circuit Court of Appeals to rule that technology alone can’t be the basis of such a stop, but that judgment does not apply everywhere, leaving people vulnerable to similar law enforcement errors.

EFF has coordinated volunteers to collect ALPR policies across the state of California and to expose agencies failing to comply with the law. EFF has also independently filed public records requests with dozens of agencies to shine light on their use of ALPR data.

We have also contacted public safety agencies whose ALPR data was exposed online, often on websites accessible to anyone with a web browser, to responsibly disclose the security vulnerabilities we found.

Nineteen volunteers (8 male) were recruited to complete a drive in the simulator equipped with a speed warning system while their eye movements were tracked. Participants had to be able to drive without glasses or contact lenses. The participants’ average age was 27.53 years, (SD = 6.32) and they had an average of 9.26 years of experience as licenced drivers (SD = 6.74). They reported an average of 175.95 km driving per week (SD = 170.05). This research complied with the tenets of the Declaration of Helsinki and was approved by the School of Psychology Research and Ethics Committee, University of Waikato (Ref 17/14).

The experiment took place in the University of Waikato fixed-base driving simulator which consisted of a complete automobile (2010 Toyota Prius plug-in) positioned in front of three angled projection surfaces. As has been described in Starkey et al. [23], the centre projection surface was located 2.32 m in front of the driver’s eye position with two peripheral surfaces connected to the central surface at 52 ° angles. This configuration produced a 178.2 ° (horizontal) by 33.7 ° (vertical) forward view of the simulated roadway from the driver’s position. The vehicle model and the simulator screens were updated at least 100 Hz. The simulator hardware and software was developed by the Transport Research Group. Its validity against on-road performance has been tested in several different kinds of experimental scenarios, including those with a focus on speed choice (e.g. [4, 5]).

Four small infra-red LEDs were placed on the outside of the car windscreen to facilitate calibration and analysis of their eye movements. The simulated speed was displayed in digital form on the dashboard. The speed warning system was implemented as an application on a smartphone attached to the console to 12 cm to the left of the steering wheel. Visually, the display was located 10.6° below, and 29.3° to the left of the driver’s forward line of sight.

A speed warning was triggered if the driver exceeded the speed limit by 4 km/h for 3 s. Speed warnings consisted of a large speed rondel (display size of 2.7 in., resolution of 1280 × 720) flashing and beeping until the participant reduced their speed to within 4 km/h of the speed limit (Fig. 1). The speed warning app had two modes, passive and active. In the passive mode, the display automatically updated to show the new speed limit after entering a new speed zone. In the active mode, the participants were told to select the new speed limit when they entered a new speed zone (from the small speed limit signs along the bottom of the display screen). If the driver forgot to select the speed, it was automatically updated to the correct speed after 7.0 s.

The display of the speed app used in the study. Above, the current speed limit is indicated by a large rondel, which also flashed as a warning to drivers exceeding the speed limit. Using the smaller rondels below, the driver was able to set the current speed limit in the Active condition

Participants drove a simulated 26.4 km rural road. The drive had two 3 km baseline sections at the beginning and end of the drive (80 km/h), and six sections with 60 km/h, 80 km/h and 100 km/h speed zones, as well as one work zone with 30 km/h (Fig. 2). It took approximately 20 mins to complete the drive. The speed warning system functioned throughout the route, except in the baseline sections (and for participants in the control condition).

The simulated road had some potential hazards, which required the driver to stay alert, including oncoming traffic, intersections with vehicles entering or exiting, roadworks and a one-way bridge and one overtaking situation, in which the driver could try to overtake a truck on a passing lane. If not, the truck pulled over on the shoulder to let the driver pass. Except for the truck, there was no other traffic in the driver’s lane.

The participants were randomly assigned either to the control group (speed warning system was turned off), or to complete the drive with the system in either the active or passive mode. The final composition of the groups is shown in Table 1. Because there were no large differences between the active and passive mode regarding the speeding or speedometer monitoring (Supplementary Tables 1 and 2), the groups were combined for analysis.

Gaze was tracked with Tobii Pro Glasses 2, a binocular head-mounted eye-tracker which could be worn like glasses. The eye tracker was calibrated using the manufacturer’s one-point calibration method, where the participant was asked to look at a marker placed on the windscreen wipers (the marker was removed before the drive). Calibration accuracy was tested qualitatively before and after a drive by asking the driver to look at designated points in the car (smartphone, speedometer, side and rear mirrors, four markers placed on the windscreen). Two participants, one from the active and one from the control group, were excluded from the analysis due to inadequate eye tracking quality.

Fixations and saccades were detected with Tobii Pro Lab 1.58 analysis software using IV-T algorithm with a velocity threshold of 100 deg/s. Such a high threshold was recommended by the manufacturer to measure periods of foveal stabilization in a dynamic environment. That is, also periods of smooth pursuit and vestibular ocular reflexes will be counted as a fixation. The speed app and speedometer areas of interests were defined for each participant. A fixation was categorised as a speedometer or speed app fixation if most of the gaze data points were within the area of interest.

The aforementioned fixations were used and their frequency and durations were already reported in Starkey et al. [23]. Because the timing of glance onsets was critical for the present analysis, we further processed the data. Glances were defined to start from the beginning of a saccade followed by a fixation to the speedometer or speed app area of interests (AOIs). Consecutive saccades/fixations within the AOI were merged within the same glance.

To measure if the drivers start to use more the speedometer when driving with a speed warning system, we calculated overall speedometer glance rates for each road section (for sections, see Fig. 2). Speedometer glance rates were calculated by dividing the number of glances by the duration of the section. For comparison, the speed app glance rates were calculated similarly. Average speeds and the proportion of time spent speeding were also calculate for each section.

Also, we wanted to understand how the speedometer glance rates in the simulator would compare to the speedometer glance rates in real-world driving. Because we were not able to find speedometer glance rates reported comparably from the literature, we calculated them ourselves using publicly available data from Lehtonen et al. [16]. Data were from an experiment, where drivers drove an instrumented car on a 2 + 2 lane motorway while their eye movements were recorded. Data from 14 drivers during their control drives without a secondary task were used. During the control drives, they were asked to keep to the inside lane and drive at 90 km/h. Nine of the drivers had driven more than 30,000 km and held a license for more than 2 years, five less than that. Recording duration was 442–510 s for 12 drivers. Two drivers only had half of the control drives recorded (234 s and 235 s). Speedometer glance rates were calculated by dividing the speedometer glance frequency by the duration of the recording.

To investigate if the speed app increased synchronization of the speedometer glances with the accelerator releases, glance data for the 30 segment before and after each accelerator release were extracted. Then the number of glances were calculated for each 1 s bin before and after a transition/warning. The corresponding speedometer glance rate was calculated by dividing the number of glances in each 1 s bin by the number accelerator releases.

To investigate if speed warnings were preceded by a period of decreased speedometer glance rate, a similar analysis was performed. Data were extracted for the 30 s segment before and after each warning. Then the number of glances and the average speed were calculated for each 1 s bin before and after a warning. The corresponding speedometer glance rate was calculated by dividing the number of glances in each 1 s bin by the number of warnings/transitions encountered. For speed warnings, the average speed in each bin, and the number of accelerator releases and brake pedal presses were also similarly counted.

We also investigated gaze and speed behaviour at speed limit transitions. Speedometer glance rates and average speed were calculated as with the speed warnings, but the speed limit transition points were used instead of the warnings. Participants in the control group did not receive any speed warnings, but their data was still included in the speed limit transition analysis.

At Roadside Technologies Ltd we offer a range of products for either hire or sale. This can aid and assist community speed watch groups in reducing vehicle speeds in residential areas. By installing a pole mounted Vehicle Activated Sign (VAS) or Speed Indication Sign (SID), it has a proven positive effect on slowing traffic down entering entrances to villages. All items are simple to use and can allow users with no previous experience equipment to monitor, measure and enforce any speed limit using similar products to what the police and councils use. We have worked with numerous CSW groups across the UK to provide traffic surveys to highlight areas of concern. Data captured in an industry standard format can then be passed on to Local Authorities for action. Take a look at our most popular options below which are all available for either hire or sale.

Our PR-1000 Speed Radar Gun is a compact, digital, simple point and shoot unit which is operational within 5 seconds of powering up. Available for either hire or sale, the user simply points the speed radar gun at traffic and the speed will show up on the LCD display fitted on the rear of the PR-1000 for the user to read. The PR-1000 will measure approaching vehicle speeds of 7-325mph at up to 400ft away from the user, making it one of the safest models available and the most popular choice for monitoring roadside speeds with community speed watch groups. The PR-1000 is ideally suited due to it"s low price point and simplicity of use. It has a recall button to show the previous 10 speed captured for data recording purposes.

The VAS-300 range is a cost-effective Vehicle Activated Sign/ Speed Indication Sign for improving road and site safety and reducing vehicle speeds on entrances to villages. Proven as an effective method to reduce traffic speeds, the VAS-300 will continually track an approaching vehicle from up to 100m away. The VAS-300 simply bolts on to a lamppost or similar object and measures and displays the approaching vehicle’s speed. Housed within the Vehicle Activated Sign is a maintenance free battery meaning it doesn’t need mains power to be operational. All units can either be powered using an existing mains supply or we can offer a solar-powered version which can keep the unit operational continuously throughout the year. The VAS-300 range has one of the most in-depth data recording facilities on the market, with the ability to covertly collect passing vehicle data, it is a very popular choice.

The SDB-18 Vehicle Activated Sign will continually track, measure and display the approaching vehicle"s speed form up to 100m away. The SDB-18 is a light weight portable Vehicle Activated Sign (VAS)/ Speed Indication Sign (SID) that can be pushed in to location by a single person. Housed within the framed work is a high intensity 12" LED Display which continually tracks and displays the approaching vehicle"s speed. Should the approaching vehicle break the speed limit, a SLOW DOWN module will illuminate to remind the driver, all the while the passing vehicle data is being covertly recorded for download at a later date. The SDB-18 collects data including the fastest and worst offenders complete with a time and date stamp. Housed within the lower part of the SDB-18 Speed Indicator Sign is a battery and solar panel which will reliably power the unit all year round without ever needing mains recharging.

The Speed Spy is a road traffic vehicle data recorder designed to covertly monitor and measure traffic flow on the highways. It simply mounts to a post or similar street furniture and measures vehicle data to show traffic flow, average speeds, 85th percentile and also the worst offending vehicles including time and date stamp.

The Speed Sentinel is the ultimate in monitoring device for measuring and recording vehicle speeds through a village. The ANPR device is fitted with a Tatille ANPR camera, once a vehicle is measured over the user selected speed limit, a picture will be taken and stored locally on the trailer or streamed over the internet to a secure file for the user to process and review. The images can then be passed to the police for review and further action. The ANPR Speed Sentinel doesn’t have H.O.T.A (Home Office Type Approval) and can"t be used as evidence. Housed within the trailer are batteries and a solar panel system to keep the trailered powered for 3-4* days.

Our superior quality 100% Australian made radar speed signs can be used for a wide range of applications for police, local councils, road workers and traffic control industries. Our experienced local engineers have specifically designed the sign to operate as simply and effectively as possible.

Drawing less than 1 amp, the radar speed check sign is robust, cost-effective and environmentally friendly. It relies on the sun’s energy for its entire operation, as well as adapting to automatic brightness changes when changing between day and night. A fantastic solution for advising motorists of speed changes and monitoring motorist speed behavior, the radar speed sign is easy to transport and set-up.

Our radar speed sign units detect and record the speed of each vehicle as it travels towards the sign, displaying a corresponding message visible for the driver to see. Our Australian engineers have designed these messages to display either a ‘smiley’ or ‘sad face’ depending on whether the vehicle is travelling at the correct speed or over-speed. An ensuing “SLOW DOWN” message will deter speeding motorists, followed by the specified speed limit.Reduces the speed of traffic by creating awareness to drivers

The electronics in today"s cars and trucks are extremely complex. However, one of the simplest devices we rely on to deliver us factual data is the speedometer. Essentially, the speedometer is powered by three independent components; the speedometer on the dashboard, the cable attached from the speedometer to the driveshaft and the speedometer sensors attached to the driveshaft to measure speed. Some speedometer issues are due to dirty or faulty sensors that relay false data through the cable and eventually show up on the dashboard.

The speedometer sensor is located in the transmission of your vehicle and is designed to register the driveshaft’s rotational speed. The sensor delivers this information through the speedometer cable and to the vehicle’s computer, which converts electrical pulses into a numerical speed. Eventually that number is displayed on the speedometer and tells you precisely how fast you are driving. If the speedometer sensor is not working properly, the speedometer will be inaccurate; potentially leading to speeding tickets or unsafe driving situations.

Whether you have a digital or manual speedometer, if it"s not displaying accurate information, it doesn"t really help you. One of the biggest signs your speedometer sensor is not working properly is the speedometer will display inaccurate readings or the needle or digital numbers will not move at all on the speedometer display. A malfunctioning speedometer sensor can also cause a speedometer to act erratically, fluctuating the reading from one speed to another; even though in reality you"re not speeding up or slowing down.

If you feel you are driving faster or slower than what the speedometer reads, it is a good idea to have your vehicle inspected by Your Mechanic, as this might be a problem with the sensor that can be repaired or an indication that the speedometer sensor needs replacement. Being proactive about repairing your speedometer issue can improve safety, not only for you, but others on the road. It can also reduce the potential of getting two citations; one for speeding and another for a damaged speedometer.

The speedometer sensor is also a critical component in the proper operation of a vehicle’s cruise control. When the sensor is not working correctly, it will not send a signal to the CPU, which impacts the vehicle’s ability to set the throttle for a desired speed. As a safety measure, automotive manufacturers engineer the cruise control in a way that if the speedometer sensor is acting up, it won"t engage the cruise control at all. On most cars sold today, this will be indicated by the cruise control light being illuminated on the dashboard - even if it"s not engaged. If you experience this problem, it"s possible that the speedometer sensor needs to be replaced.

The speedometer sensor is located inside the transmission and attached to a driveshaft, which impacts multiple functions of the car. Due to this fact, it"s possible that the Check Engine Light will light up on the dashboard if a sensor problem is discovered by the vehicle"s CPU. Regardless of why the check engine light is illuminated, it"s never a good thing, nor should it be avoided. If the check engine light shows up anytime, contact a mechanic as soon as possible so they can diagnose the problem with the correct diagnostic tools. Sometimes the issue is small and the CPU needs to be reset; but don"t take that risk.

Today"s cars and trucks have electronic fuel injection, which is controlled by the onboard computer. The EFI supplies fuel to the engine based on input from multiple sensors; one of which is the speedometer sensor. If you notice that your car starts to lose power; especially when you apply pressure to the throttle, this might be caused by a damaged or malfunctioning speedometer sensor. This problem could be potentially harmful to other mechanical components on your vehicle, so don"t ignore the issue. Contact a certified mechanic as soon as possible to determine what is causing this issue.

As you can see, the speedometer sensor impacts the operation of multiple components that allows you to efficiently operate your car or truck. Anytime you experience any of the above warning signs, contact a professional mechanic to properly diagnose and repair the issue.

A speedometer or speed meter is a gauge that measures and displays the instantaneous speed of a vehicle. Now universally fitted to motor vehicles, they started to be available as options in the early 20th century, and as standard equipment from about 1910 onwards.pit log, while aircraft use an airspeed indicator.

The speedometer was originally patented by Josip Belušić (Giuseppe Bellussich) in 1888. He presented his invention at the 1889 Exposition Universelle in Paris. His invention had a pointer and a magnet, using electricity to work.

Many speedometers use a rotating flexible cable driven by gearing linked to the vehicle"s transmission. The early Volkswagen Beetle and many motorcycles, however, use a cable driven from a front wheel.

Some early mechanical speedometers operated on the governor principle where a rotating weight acting against a spring moved further out as the speed increased, similar to the governor used on steam engines. This movement was transferred to the pointer to indicate speed.

This was followed by the Chronometric speedometer where the distance traveled was measured over a precise interval of time (Some Smiths speedometers used 3/4 of a second) measured by an escapement. This was transferred to the speedometer pointer. The chronometric speedometer is tolerant of vibration and was used in motorcycles up to the 1970s.

When the vehicle is in motion, a speedometer gear assembly turns a speedometer cable, which then turns the speedometer mechanism itself. A small permanent magnet affixed to the speedometer cable interacts with a small aluminium cup (called a speedcup) attached to the shaft of the pointer on the analogue speedometer instrument. As the magnet rotates near the cup, the changing magnetic field produces eddy current in the cup, which itself produces another magnetic field. The effect is that the magnet exerts a torque on the cup, "dragging" it, and thus the speedometer pointer, in the direction of its rotation with no mechanical connection between them.

The pointer shaft is held toward zero by a fine torsion spring. The torque on the cup increases with the speed of rotation of the magnet. Thus an increase in the speed of the car will twist the cup and speedometer pointer against the spring. The cup and pointer will turn until the torque of the eddy currents on the cup are balanced by the opposing torque of the spring, and then stop. Given the torque on the cup is proportional to the car"s speed, and the spring"s deflection is proportional to the torque, the angle of the pointer is also proportional to the speed, so that equally spaced markers on the dial can be used for gaps in speed. At a given speed, the pointer will remain motionless and point to the appropriate number on the speedometer"s dial.

The return spring is calibrated such that a given revolution speed of the cable corresponds to a specific speed indication on the speedometer. This calibration must take into account several factors, including ratios of the tail shaft gears that drive the flexible cable, the final drive ratio in the differential, and the diameter of the driven tires.

One of the key disadvantages of the eddy current speedometer is that it cannot show the vehicle speed when running in reverse gear since the cup would turn in the opposite direction – in this scenario the needle would be driven against its mechanical stop pin on the zero position.

Many modern speedometers are electronic. In designs derived from earlier eddy-current models, a rotation sensor mounted in the transmission delivers a series of electronic pulses whose frequency corresponds to the (average) rotational speed of the driveshaft, and therefore the vehicle"s speed, assuming the wheels have full traction. The sensor is typically a set of one or more magnets mounted on the output shaft or (in transaxles) differential crown wheel, or a toothed metal disk positioned between a magnet and a magnetic field sensor. As the part in question turns, the magnets or teeth pass beneath the sensor, each time producing a pulse in the sensor as they affect the strength of the magnetic field it is measuring.CAN Bus. Most modern electronic speedometers have the additional ability over the eddy current type to show the vehicle"s speed when moving in reverse gear.

A computer converts the pulses to a speed and displays this speed on an electronically controlled, analogue-style needle or a digital display. Pulse information is also used for a variety of other purposes by the ECU or full-vehicle control system, e.g. triggering ABS or traction control, calculating average trip speed, or increment the odometer in place of it being turned directly by the speedometer cable.

Another early form of electronic speedometer relies upon the interaction between a precision watch mechanism and a mechanical pulsator driven by the car"s wheel or transmission. The watch mechanism endeavours to push the speedometer pointer toward zero, while the vehicle-driven pulsator tries to push it toward infinity. The position of the speedometer pointer reflects the relative magnitudes of the outputs of the two mechanisms.

Typical bicycle speedometers measure the time between each wheel revolution and give a readout on a small, handlebar-mounted digital display. The sensor is mounted on the bike at a fixed location, pulsing when the spoke-mounted magnet passes by. In this way, it is analogous to an electronic car speedometer using pulses from an ABS sensor, but with a much cruder time/distance resolution – typically one pulse/display update per revolution, or as seldom as once every 2–3 seconds at low speed with a 26-inch (660 mm) wheel. However, this is rarely a critical problem, and the system provides frequent updates at higher road speeds where the information is of more importance. The low pulse frequency also has little impact on measurement accuracy, as these digital devices can be programmed by wheel size, or additionally by wheel or tire circumference to make distance measurements more accurate and precise than a typical motor vehicle gauge. However these devices carry some minor disadvantages in requiring power from batteries that must be replaced every so often in the receiver (and sensor, for wireless models), and, in wired models, the signal is carried by a thin cable that is much less robust than that used for brakes, gears, or cabled speedometers.

Other, usually older bicycle speedometers are cable driven from one or other wheel, as in the motorcycle speedometers described above. These do not require battery power, but can be relatively bulky and heavy, and may be less accurate. The turning force at the wheel may be provided either from a gearing system at the hub (making use of the presence of e.g. a hub brake, cylinder gear, or dynamo) as per a typical motorcycle, or with a friction wheel device that pushes against the outer edge of the rim (same position as rim brakes, but on the opposite edge of the fork) or the sidewall of the tire itself. The former type is quite reliable and low maintenance but needs a gauge and hub gearing properly matched to the rim and tire size, whereas the latter requires little or no calibration for a moderately accurate readout (with standard tires, the "distance" covered in each wheel rotation by a friction wheel set against the rim should scale fairly linearly with wheel size, almost as if it were rolling along the ground itself) but are unsuitable for off-road use, and must be kept properly tensioned and clean of road dirt to avoid slipping or jamming.

Excessive speedometer errors after manufacture, can come from several causes but most commonly is due to nonstandard tire diameter, in which case the error is:

For example, a standard tire is "185/70R14" with diameter = 2*185*(70/100)+(14*25.4) = 614.6 mm (185x70/1270 + 14 = 24.20 in). Another is "195/50R15" with 2*195*(50/100)+(15*25.4) = 576.0 mm (195x50/1270 + 15 = 22.68 in). Replacing the first tire (and wheels) with the second (on 15" = 381 mm wheels), a speedometer reads 100 * ((614.6/576) - 1) = 100 * (24.20/22.68 - 1) = 6.7% higher than the actual speed. At an actual speed of 100 km/h (60 mph), the speedometer will indicate 100 x 1.067 = 106.7 km/h (60 * 1.067 = 64.02 mph), approximately.

In many countries the legislated error in speedometer readings is ultimately governed by the United Nations Economic Commission for Europe (UNECE) Regulation 39,

The indicated speed must never be less than the actual speed, i.e. it should not be possible to inadvertently speed because of an incorrect speedometer reading.

The indicated speed must not be more than 110 per cent of the true speed plus 4 km/h (2.5 mph) at specified test speeds. For example, at 80 km/h (50 mph), the indicated speed must be no more than 92 km/h (57 mph).

The standards specify both the limits on accuracy and many of the details of how it should be measured during the approvals process. For example, the test measurements should be made (for most vehicles) at 40, 80 and 120 km/h (25, 50 and 75 mph), and at a particular ambient temperature and road surface. There are slight differences between the different standards, for example in the minimum accuracy of the equipment measuring the true speed of the vehicle.

The UNECE regulation relaxes the requirements for vehicles mass-produced following type approval. At Conformity of Production Audits the upper limit on indicated speed is increased to 110 per cent plus 6 km/h (3.7 mph) for cars, buses, trucks, and similar vehicles, and 110 per cent plus 8 km/h (5.0 mph) for two- or three-wheeled vehicles that have a maximum speed above 50 km/h (31 mph) (or a cylinder capacity, if powered by a heat engine, of more than 50 cm3 (3.1 cu in)). European Union Directive 2000/7/EC, which relates to two- and three-wheeled vehicles, provides similar slightly relaxed limits in production.

There were no Australian Design Rules in place for speedometers in Australia before July 1988. They had to be introduced when speed cameras were first used. This means there are no legally accurate speedometers for these older vehicles. All vehicles manufactured on or after 1 July 2007, and all models of vehicle introduced on or after 1 July 2006, must conform to UNECE Regulation 39.

The speedometers in vehicles manufactured before these dates but after 1 July 1995 (or 1 January 1995 for forward control passenger vehicles and off-road passenger vehicles) must conform to the previous Australian design rule. This specifies that they need only display the speed to an accuracy of ±10% at speeds above 40 km/h, and there is no specified accuracy at all for speeds below 40 km/h.

The amended Road Vehicles (Construction and Use) Regulations 1986 permits the use of speedometers that meet either the requirements of EC Council Directive 75/443 (as amended by Directive 97/39) or UNECE Regulation 39.

Starting with U.S. automobiles manufactured on or after 1 September 1979, the NHTSA required speedometers to have a special emphasis on 55 mph and display no more than a maximum speed of 85 mph. On 25 March 1982, the NHTSA revoked the rule because no "significant safety benefits" could come from maintaining the standard.

The first and simpler method is based on how far the receiver has moved since the last measurement. Such speed calculations are not subject to the same sources of error as the vehicle"s speedometer (wheel size, transmission/drive ratios). Instead, the GPS"s positional accuracy, and therefore the accuracy of its calculated speed, is dependent on the satellite signal quality at the time. Speed calculations will be more accurate at higher speeds when the ratio of positional error to positional change is lower. The GPS software may also use a moving average calculation to reduce error. Some GPS devices do not take into account the vertical position of the car so will under-report the speed by the road"s gradient.

As mentioned in the satnav article, GPS data has been used to overturn a speeding ticket; the GPS logs showed the defendant traveling below the speed limit when they were ticketed. That the data came from a GPS device was likely less important than the fact that it was logged; logs from the vehicle"s speedometer could likely have been used instead, had they existed.

A person who receives a payable traffic citation must comply with the citation by completing one of the following options within 30 days after receipt of the citation:

Check "request a Payment Plan" for each violation in which a payment plan is requested, sign, date at the bottom of the ticket and mail the form within 30 days to the address shown as soon as possible.

If you fail to comply with one of the four options WITHIN 30 DAYS after receipt of a payable traffic citation, the Motor Vehicle Administration will be notified and may take action to suspend your driver"s license. DRIVING ON A SUSPENDED LICENSE IS A CRIMINAL OFFENSE FOR WHICH YOU COULD BE INCARCERATED.

Traffic Citations - Handwritten and Electronic Traffic citations in the State of MD are issued in one of two different ways - a handwritten version or an electronic version. When you are charged with a payable traffic offense, the officer will give you two copies of the handwritten version of the traffic citation. If the citation was issued electronically, the officer prints you a copy from the officer"s patrol car.

There are two types of traffic violations in Maryland, "payable" and “must appear". “Must appear” violations, such as driving while under the influence of alcohol or drugs or driving on a suspended license are not covered in this fact sheet. Drivers who receive "Must Appear" citations or have payable citations included with a "Must Appear" citation, will continue to receive automatic trial date notices. For more information about “must appear” traffic offenses, contact the District Court location nearest you or the District Court Traffic Processing Center via Telephone: 1-800-492-2656 or 410-260-1093.

Payable traffic violations for example, a speeding ticket or failing to stop for a school bus, are those you may choose to plead “guilty” to and pay a fine without appearing in court. You have a payable violation when the officer checks the second box under “Notice to Appear”on your handwritten citation or the "Payable Fine" box on the electronic version. Payable traffic violations are not punishable by jail time.

You have four options when confronted with a payable traffic citation (1) paying the fine, (2) requesting to enter into a payment plan (3) pleading “guilty with an explanation” and appearing for a waiver hearing or (4) requesting a trial date andappearing for trial. If you choose not to pay the fine, you must request either a waiver hearing or a trial, at which you will be required to appear in person to dispose of your case. If you do not respond WITHIN 30 DAYS to one of the four options, MVA will be notified and may take action to suspend your license. Driving on a suspended license is a criminal offense for which you could be incarcerated.

• Visit the District Court location nearest you and pay the fine at the cashier’s office. If you choose to pay with a credit card, a service charge will be added to your fine.

•Mail your check or money order to the District Court of MD with the Return to Court copy in the envelope attached to the handwritten version of the traffic citation. If you received more than one citation you may place all citations in the same envelope. If you received a copy of an electronic traffic citation, cut on the dotted line and mail the Option Form to the address below. To ensure proper credit, please include the citation number on your payment.

*Call the District Court’s Interactive Voice Response (IVR) system at 1-800-492-2656. The system will provide directions to court locations and other information. The IVR system also accepts credit card payments for traffic citations, through Visa, Master Card, Discover, and American Express. Your credit card company will assess a service charge for each citation when you pay by phone. If you want to request a trial date or a waiver hearing date, DO NOT PAY THE FINE. See the instructions for Requesting a Waiver Hearing or Requesting a Trial Date below.

Check ""Request a Payment Plan" for each violation in which a payment plan is requested, sign, date at the bottom of the ticket and mail the form within 30 days to the address shown on the ticket as soon as possible.

If you choose to plead guilty and would like to request that your fine be reduced or waived or that you be given probation rather than a conviction, you must make your request WITHIN 30 DAYS of receipt of your citation. Check the "Request Waiver Hearing" option box on the Return to Court copy of the handwritten citation and envelope or the electronic version Option Form, sign, date and mail it to:

The hearing presents you with an opportunity to explain to the judge why you committed the offense and request that your fine be reduced or waived or ask that you be given probation rather than a conviction because of extenuating circumstances. Lowering your fine is at the discretion of the judge. There is a possibility that your fine could be increased, up to a maximum of $500. If the judge renders a guilty verdict, you have the right to an appeal. There are non-refundable court costs for filing an appeal. (A "probation before judgment" cannot be appealed.)

WITHIN 30 DAYS of receipt of your citation,check the "Request a Trial" option box on the Return to Court copy and envelope, or the electronic version Option Form, sign, date, and mail it to:

It may take several weeks for a trial date to be scheduled. If you do not receive a trial date within six weeks, contact the District Court in the county in which you received the ticket.

At your trial, the officer who issued your ticket will testify, and you will have an opportunity to present your side of the case. After hearing both sides, the judge will render a decision. You have the right to an appeal within 30 days of your trial date, if you are found guilty. There are non-refundable court costs for filing an appeal.

The post office will not forward Court mail, and updating your address with MVA does not update your address with the Court.(The District Court is unable to conduct official court business through e-mail.)

If you have lost or misplaced your traffic citationuse the option form provided here. Follow the instructions for completing the form, select your option, print, date, sign, and return the form to the Traffic Processing Center within 30 days after receipt of the citation. Use the Judiciary"s Online Case Search to access information such as citation number, fine amount, date of the violation, and county in which you received the citation in order to have your payment or request applied correctly. For other types of citations, see below.

If you wish to request a change in the trial date, submit your request in writing to the District Court where your trial or hearing will be heard with an explanation of the circumstances that require the change and include any supporting documentation. Your request is not automatically granted; it is up to a judge to determine whether to change your trial date.

If you fail to appear for trial, the MVA will be notified and will take action to suspend your license. Driving on a suspended license is a criminal offense for which you can receive jail time. If you only have one failure to appear, you can request and receive a new trial or hearing date. Put your request for a new trial or hearing to plead guilty with an explanation in writing. Mail or submit your request to the court where your original trial date was set.

The red light, speed monitoring, school bus monitoring, and electronic toll cameras are installed and/or operated at the expense and direction of the locality or municipality or, if on a state highway or toll facility, by the Department of State Police or Maryland Transportation Authority. Complaints about the location or operation of these cameras should be sent to the address on the citation. In most cases this is the address of the police or state agency. Please note: these citations are not found on the Judiciary"s Case Search and if a ticket was lost - please contact the local jurisdiction where you received the ticket, the Maryland State Police if on a state highway, or the Maryland Transportation Authority if it was a toll violation.

As stated on the red light, speed monitoring, school bus monitoring, and electronic toll violation citations: "Payment of the penalty amount for the violation will not result in points and cannot be used to increase your insurance rates."

Various vendors manufacture the cameras used in red light, speed monitoring, school bus, and electronic toll traffic programs. For information on how these cameras operate, contact the local police department in the municipality where the camera is located or, if on a state highway or toll facility, the Maryland State Police or Maryland Transportation Authority.

In traffic cases, you may plead "guilty with an explanation" and appear for a hearing. The hearing presents you with an opportunity to explain to the judge why you committed the offense and request that your fine be reduced or waived or ask that you be given probation rather than a conviction because of extenuating circumstances. Lowering your fine is at the discretion of the judge. There is a possibility that your fine could be increased, up to a maximum of $500. If the judge renders a guilty verdict, you have the right to an appeal. There are non-refundable court costs for filing an appeal. If you wish to plead "not guilty," you must request and appear for a trial where the officer and any witnesses will be present.

Stet. A suspension of the prosecution. The State may reopen the case without the need for the defendant to be recharged. A case may be reopened because of the defendant’s arrest on additional charges or his/her failure to live up to some agreed-to-condition within a reasonable time after the entry of the stet.