Effects of heavy trucks on cyclists during overtaking manoeuvres: a controlled study

Since December 2023, so-called High-Capacity Transport vehicles (up to 34.5 m length) are allowed on parts of the Swedish network of primarily divided roads. Investigations are ongoing under which premises longer HCT vehicles can be allowed on undivided rural roads, where cyclists and other active travellers may be present. On rural roads, overtaking manoeuvres are a frequently occurring encounter between cyclists and motorists. The fear related to dangerous overtakes is a major deterrent to rural cycling, and the aerodynamic load generated especially by large vehicles may pose a danger in that it could affect cyclist stability. To systematically investigate the effects of lateral distance, overtaking vehicle speed and truck length on cyclists stability and perception of discomfort, a controlled study was conducted in a laboratory setting. In a 700 m long tent, 23 experienced road cyclists rode on free rollers while being overtaken by a 16.5 m and a 32.5 m long truck combination at 50 and 80 km/h, with lateral distances of 1 m, 1.5 m and 2 m. Additionally, a reference overtake was run, reflecting a full lane change at reduced speed (16.5 m truck, 50 km/h, 3.5 m). Lateral distance had the largest impact on aerodynamic load and discomfort ratings, followed by speed. The length of the truck only had a minor effect. The cyclists’ lateral position on the rollers was not affected by any of the three factors, but increased slightly from before to during to after the overtaking manoeuvre, regardless of the condition. Based on these findings, a full lane change is recommended when overtaking cyclists. To which extent a speed adaptation is appropriate as compensatory measure needs to be investigated further.