Dense automatic speed enforcement effectively reduces speeding

A recent before-after study supports the earlier concept that automatic speed enforcement is an effective measure for reducing driving speeds and thus improving road safety. Since the introduction of automatic speed enforcement on a highway in Finland, the average share of vehicles speeding by over 10 km/h was reduced from 11% to 2%.

Car passing an automatic speed camera

Photo: Mostphotos

Ring Road I (highway 101) in Finland is one of the most highly trafficked roads in the country. Accidents and congestion occur regularly on the roughly 25 km stretch of road circulating the city of Helsinki. At the start of February 2016, automatic speed enforcement was installed on the road as a safety measure, with speed control points installed densely at 15 locations. Drivers passes a control point every 3 km, roughly 10% of which were equipped with a camera.

Due to the characteristics of the road, a separate before-after study was carried out to analyse the impacts of the enforcement on driving speed, other characteristics of the traffic flow, traffic accidents and road users’ opinions.

Roadworks complicated the study

Right after the introduction of automatic speed enforcement, major roadworks began at several locations along the road. It was attempted to mitigate the effects of the roadworks by careful selection of measurement points and road sections for comparison. During the study, changes were also made to the legislation for imposing fines; the petty fine was doubled in September 2015, and the speeding limit for imposing a petty fine was reduced from 8 km/h to 7 km/h in October 2016.

Reduced driving speeds and speeding

The impact of the automatic speed enforcement on driving speeds was studied from spot speeds at automatic traffic measurements spots (LAM spots), Police data on speeding, travel-time measurements on different sections, and spot speed measurements at one location. Following the introduction of automatic speed enforcement, the share of vehicles speeding by more than 10 km/h fell from around 11% to 2%. Average spot speeds dropped by 2–5 km/h at the LAM spots, and travel-times increased by around 1–7 seconds on the different road sections. Consequently, speed differences between vehicles also decreased, since speeding diminished overall and over-speeds were less severe. Before the installation of automatic speed enforcement, at one LAM spot around 60% of vehicles drove over the allowed speed limit, compared to only 30% after installation (Figure 1). No kangaroo effect, i.e. decelerating at speed control cameras, seemed to occur, possibly because of the dense placement of speed control points.

Figure 1

Figure 1. Distribution of vehicle speeds at a LAM spot (situated 700 m from the nearest speed control point, speed limit 80km/h) before and after installation of automatic speed enforcement.

Traffic accidents seem to have decreased

The roadworks complicated the collection of statistically reliable accident data, with only two months being fully comparable. However, the number of traffic accidents seems to have dropped on Ring Road I since the introduction of automatic speed enforcement. After the roadworks began, traffic accidents increased on the affected road sections but decreased elsewhere on the road. The impact of automatic speed enforcement on traffic accidents was also estimated based on the reduction of speed, using the Power Model developed by Göran Nilsson in 1981. It was estimated that after the introduction of automatic speed enforcement, the number of injury accidents fell by 6–15% on road sections without roadworks. In terms of annual savings to society, the decreased accident rate was estimated to be €1.5–2.2 million.

Road users support automatic speed enforcement

Interviews with road users were carried out in shopping malls along Ring Road I before and after the installation of automatic speed enforcement. A clear majority (2015: 78% vs. 2016: 72%) of those interviewed had a positive attitude towards automatic speed enforcement in general. However, the level of support specific to Ring Road I decreased (2015: 67% vs. 2016: 55%), probably due to the roadworks which happened to start right after the introduction of automatic speed enforcement.

The full report  is available on the homepage of the Finnish Transport Safety Agency (written in Finnish, with a summary in Swedish and English): https://www.trafi.fi/tietopalvelut/julkaisut/2017_tutkimukset/keha_i_n_automaattinen_nopeusvalvonta

Fanny MalinContact
Fanny Malin
fanny.malin@vtt.fi
VTT, Finland

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