Results from a VTI study investigating traffic safety effects on roads that have been equipped with milled rumble strips in the middle of the road give that the severity consequence per accident has declined with about 11 per cent. The rate of fatalities or seriously injured road users, the FSI-rate, in principle remained unchanged. The FSI-rate for single accidents decreased by more than 7 per cent and the total personal injury accident rate increased by 18 per cent. The most important group of roads for the actual measure consists of two lane roads below 10 metres in road width. For these road types the FSI-rate has decreased. For the two road width classes, narrow two lane (< 8 metres) and normal two lane (8—10 metres) with speed limit 90 km/h, the following results are obtained: • Narrow two lane roads, below 8 metres, have an observed reduction of the FSI-rate of slightly less than 30 per cent and a reduction in severity consequence of slightly more than 30 per cent. • Normal two lane roads, 8—10 metres, have a reduced FSI-rate with 7 per cent and a reduction in severity consequence with slightly more than 20 per cent. The personal accident rate has increased by 18 per cent. • The reduction in FSI-rate for 8—10 metre roads is observed for running off accidents, which has a reduction of almost 18 per cent for this road type. • If a special analysis is done for single accidents with the assumption that all effect is to be found in running off to the left, it would be about 35 per cent reduction for running off to the left accidents on 8—10 metre roads. This result is in good agreement with results from a similar Finnish study. It shall be noted that the results are uncertain due to a low level of accidents. Continued evaluation should be conducted during 2012 to obtain more reliable results. The main purpose with milled central rumble strips is to "wake up" drivers who for some reason unintentionally are starting to pass the middle line. Earlier studies abroad and Swedish in-depth fatal accident studies indicate that this measure would have a positive safety effect, especially on running off the road to the left and head-on accidents. (Author/publisher) This report may be accessed by Internet users at http://www.vti.se/en/publications/traffic-safety-effects-of-milled-rumb…
Abstract