In Japan, the speed of vehicles on residential roads (roads used mainly by local residents for their daily activities) is in principle limited to 30 km/h. Various measures such as the introduction of Zone 30 have also been taken to limit driving speeds. However, even in areas designated as Zone 30, there is a constant flow of vehicles running in over the speed limit. If driving speeds could be measured accurately and inexpensively, there are many situations where this would be useful, such as speed surveys on residential roads.
Therefore, this study attempted to develop an inexpensive speed measurement system by connecting a laser distance sensor with high measurement accuracy to a small PC.
The speed measurement method is as follows. A laser is irradiated at an angle to the running vehicle from outside the roadway. The measurement distance is constant while the sides of the vehicle are irradiated and changes while the front or rear of the vehicle is irradiated. The distance to the front or rear of the vehicle, the laser irradiation angle and the three-square theorem are then used to determine the change in distance in the direction of the driving, and a regression analysis is applied in relation to the time of measurement to calculate the driving speed.
It was confirmed that the error between the speed obtained by measuring from an angle and the speed measured from the front was small. In addition, it was confirmed that the speed of vehicles running continuously can also be measured. Furthermore, the frequency of the laser irradiation used in this study was about 70 Hz, and it was confirmed that the speed of a vehicle running at about 70 km/h could be observed with high accuracy.

speed measurement; device development