Safety Effects of Advisory Cycle Lanes (2–1 Roads): Evidence from Overtaking Behaviour, Traffic Monitoring and Before-and-After Crash Analysis

In recent years, increasing attention has been devoted to improving cyclists’ safety in road traffic, particularly on roads without separated cycling infrastructure. Advisory cycle lanes (2–1 roads) have recently been introduced in several European countries on narrow roads where conventional cycling facilities cannot be provided. However, evidence regarding their safety effects remains limited. This paper evaluates the effects of advisory cycle lanes on overtaking behaviour and crash occurrence on selected roads in and around Maribor, Slovenia. The study combines OpenBikeSensor measurements of lateral passing distance (open-source hardware; OpenBikeSensor e. V., Stuttgart, Germany), traffic volume and speed data, and a before-and-after analysis of police-reported crashes. In total, 970 overtaking manoeuvres were recorded on six streets with advisory lanes and comparable control streets without cycling infrastructure. Advisory bike lanes were associated with greater lateral passing distances, with mean clearance increasing from 135 cm to 156 cm. Nevertheless, around 40–50% of overtakes still occurred within 1.5 m of the cyclist. Crash analysis indicated reductions of about 22% in total crashes and 38% in cyclist-involved crashes, although the small number of crashes warrants cautious interpretation. The collected data enable a comparison of traffic behaviour and safety effects of advisory cycle lanes in Slovenia, providing a basis for future planning of traffic infrastructure aimed at improving the coexistence of cyclists and motor vehicle drivers.