The OBU is made of three components:

1. Display and loudspeaker placed in the air nozzle. The display shows the speed limit, penalty points for the actual trip and the total number of penalty points.
2. GPS/GPRS unit with a memory card where the digital speed map is stored. The unit is placed under the dashboard.
3. External GPS antenna placed behind the rear-view mirror.

The system works in the following way:

Each second the OBU receives a position from the GPS. The OBU calculates a position on the digital map, using a special technique called map matching, and displays the actual speed limit. The system then compares  the speed limit with the actual car speed.  If the car exceeds the speed limit by more than 5 km/h, the OBU gives the driver a verbal warning e. g. “50 – you are driving too fast”.  The warning is repeated every 6. second unless the speed is lowered to the actual criterion. After the second warning the system starts to calculate penalty points. The number of penalty points are related to the amount of the speeding. Penalty points for the actual trip are displayed in the lower right corner of the display, and the total number for the full period in the lover left corner of the display.

For every map matched position, the system also calculates the quality of the map matching. If the quality is too low the speed limit is shown on the display in brackets, and the system does not react on speeding. The map matching algorithm developed for the project has many parameters tuned for specific map and shows high accuracy and performance.

After each trip the OBU uploads a log file to the web server, if penalty points were earned during the trip. At nights the OBU uploads an error log where, amongst other thing, attempt on cheating is logged. The OBU also upload a one second log; this log is used for research purposes. During the night connection the server also uploads software updates, modifications to the digital speed map and corrections to the penalty points to active OBU’s. Another option is to use the OBU for tracking stolen cars. Test drivers can call our hot line: By sending a SMS to the OBU, the OBU will return the position of the car.

Drivers can log in to a personalized project web page and see where and why penalty points have been calculated. The screen dump below shows a driver, who has driven in the northern direction on the motorway the 7th June 2006 at 19:44 when he got penalty points. The speed limit on this place is 90 km/h according to the system. He had got points four times with 6 second in between. The first time he got one point because his speed was 107, the second and the third time he got two points because his speed was respectively 112 and 111 (the number of points depends on the size of the speeding) the fourth time he had slowed down to 102 and he got only one point. Thus, the web page gives test drivers an opportunity to control the system. They can check their speeding and report the errors if any occurs.

Updated on June 17, 2007 20:45.