Speed-calming measures and their effect on driving speed - Test of a new technique measuring speeds based on GNSS data

- Speed humps and chicanes are widespread speed-calming measures.
- Humps and chicanes have virtually the same reducing effect on mean speed.
- Chicanes reduce speed variation less than humps and might therefore be a less safe measure.

Speeding increases the risk and severity of accidents, especially for vulnerable road users. Hence, minimisation of speeding in built-up areas is vital. Some countries widely use speed-calming measures (SCs). Documentation shows that SCs reduce speeding considerably although various types and designs of SCs affect this reduction. This paper includes studies of the effects from establishment of sinus speed humps of height 10 cm and length 950 cm and chicanes (with a free carriageway width of 5.30 cm and a length between the 0.5 m wide obstacles of 18 m) as a before/after study where the speed pattern after establishing SCs is compared with the one before. Floating Car Data used for analyses includes 3216 trips passing one/more SCs. The main results are that the effect from SCs decreases with the distance from the SCs and that a clear pattern is hard to establish above 75 m from the SC. Despite the apparent absence of more distant effects of each SC, there is an overall reduced average speed on the full length of a road with SCs. Humps reduce the mean speed comparable to the reduction from chicanes, but the speed variation is less reduced near chicanes, and especially prior to the arrival to such SC. Due to different traffic patterns around the two types of SCs, a direct comparison between the effects from humps and chicanes cannot be made. A tentative result at least for the two types of SCs studied is that the chicane results in a reduced effect on speed variation compared to the hump. The chicanes result in increased speed variation prior to the arrival to the SC compared to the humps. Hence, the indication is that chicanes might be less safe than humps due to speed variation although more research is needed especially concerning developing of best practice design for speed reducing devices and other speed-calming measures in built-up areas.