Previous studies have shown that time to arrival estimates (TTA) as well as accepted gap size are influenced by vehicle size. Drivers tend to choose smaller gaps and provide longer TTA estimates when confronted with smaller vehicles compared to larger ones. Object size alone, as well as the potential threat ascribed to the approaching vehicle, have been suggested as being the factors that underlie this bias. To assess the merit of these potential explanations, we used different types of two-wheelers (bicycle, e-bike, scooter) of roughly the same size, but substantial differences in the potential threat they pose. Participants saw videos of approaching two-wheelers and were required to either indicate the smallest acceptable gap, or to estimate TTA (two blocks). Participants accepted smaller gaps for the two bicycle types than for the scooter. Likewise, TTA estimates for the two bicycles were longer than for the scooter. These results indicate that certain characteristics of the vehicle unrelated to physical size, such as the potential threat the vehicle poses, play a role in the assessment of a vehicle’s approach. This implies that other road users might select potentially risky gaps when turning in front of bicycles and e-bikes in traffic.