Instruments for speed control

In Germany, only verified speedometers may be used for official traffic control. Prerequisite for each verification is that the respective instrument type has been pattern-approved for verification by the Physikalisch-Technische Bundesanstalt. The majority of instruments used in Germany applies one of the measuring principles described in the following in simplified terms.

The radar beams emitted by the instrument are reflected by the vehicle; due to the Doppler effect, the frequency of the reflected beam is higher (when the vehicle approaches the instrument) or lower (when the vehicle moves away from the instrument) than the frequency of the emitted beam. The instrument receives part of the reflected radiation, measures the difference between both frequencies and calculates the vehicle speed on this basis. List of verified instruments

Several light barriers aligned across the roadway are installed one behind the other with a known spacing between them. When the light barrier is interrupted, the vehicle generates an electric signal; the instrument measures the time intervals between the signals and calculates the vehicle speed, taking the distance into account. List of verified instruments

Several piezo sensors designed as coaxial cables are placed into the roadway one behind the other, with a known spacing between them. The vehicle generates an electric signal whenever it passes across a sensor; the instrument measures the time intervals between the signals and calculates the vehicle speed, taking the distance into account. List of verified instruments

Fibre-optic sensors make use of the effect, that the transfer attenuation goes up by the pressure of a driving over vehicle. Several fibre-optic sensors are placed into the roadway one behind the other, with a known spacing between them. The vehicle generates an optical signal whenever it passes across a sensor; the instrument measures the time intervals between the signals and calculates the vehicle speed, taking the distance into account. List of verified intruments

Several induction loops are placed into the roadway one behind the other, with a known spacing between them. The vehicle generates an electric signal whenever it passes across a sensor; the instrument measures the time intervals between the signals and calculates the vehicle speed, taking the distance into account. List of verified instruments

The speed of vehicles is determined as the change in their distance in the direction of travel, which takes place during a fixed measurement time. The operator aims at the vehicle, the instrument emits a series of laser pulses and receives those reflected by the vehicle. For each of these pulses the time is measured which passes until the pulse is received again, and this time is used to calculate the respective distance from the vehicle taking the well-known light velocity as a basis. From the change in the distance determined in this way follows the vehicle speed as the result of an adjustment calculus (in the most simple case: slope of a fitted line). List of verified instruments

Laser scanners are multi-object capable, ie they allow measurement of the speed on multiple lanes. The roadside speed monitoring unit established for this purpose scans the entire area of ​​the road over several lanes away from horizontal and records the movements of all vehicles while driving past. During the scan, the device sends out each short laser pulses and receives the reflected portion of each vehicle. For each of these pulses, the transit time is measured until the arrival of re-order them using the known speed of light to calculate the corresponding distance to the vehicle. The distance measurements and the scan will be performed at a high repetition rate. The vehicles are pursued (tracking). From the change of the so-measured distance of a tracked vehicle over time is then determined the velocity measurement that can be unambiguously assigned to this vehicle. List of verified intruments

Video traffic control systems are used in police cars which participate in the moving traffic as do the cars to be controlled. To measure a vehicle's speed, the time it takes for a vehicle to cover a defined distance is manually stopped. The distance is measured in advance and input in the device or determined on the basis of the turns of the police car wheels while it drives behind the car to be controlled. The instrument then automatically calculates the resulting average speed. List of verified instruments

Geschwindigkeitsüberwachungsanlagen zur Abschnittskontrolle dienen der Erfassung und Dokumentation von Geschwindigkeitsverstößen auf einem festen Streckenabschnitt bekannter Länge bei der amtlichen Verkehrsüberwachung. Hierzu verfügt die Geschwindigkeitsüberwachungsanlage über einen Ein- und einen Ausfahrtsquerschnitt, welche das betreffende Fahrzeug am Beginn bzw. am Ende des überwachten Streckenabschnitts innerhalb eines definierten Messfeldes erfassen. Aus der zwischen dem Passieren des Ein- und des Ausfahrtsquerschnitts liegenden Zeitdifferenz und der bekannten Länge des Streckenabschnitts ergibt sich der Wert der vorzuwerfenden Durchschnittsgeschwindigkeit. Überschreitet der Wert der vorzuwerfenden Durchschnittsgeschwindigkeit einen am Gerät frei einstellbaren Grenzwert, so erfolgt hinter dem Ausfahrtsquerschnitt eine Frontfotoaufnahme zur Fahreridentifizierung.

Liste der zugelassenen bzw. konformitätsbewerteten Geräte

The following list shows the most important approved instruments, including the measuring principle applied, and the addresses of the manufacturers or of the German distributor (last change: july 2007):