High- and Low-Order Overtaking-Ability Affordances

Abstract

Objective:

The aim of this study was to answer the question, Do drivers take into account the action boundaries of their car when overtaking?

Background:

The Morice et al. affordance-based approach to visually guided overtaking suggests that the “overtake-ability” affordance can be formalized as the ratio of the “minimum satisfying velocity” (MSV) of the maneuver to the maximum velocity (V_max) of the driven car. In this definition, however, the maximum acceleration (A_max) of the vehicle is ignored. We hypothesize that drivers may be sensitive to an affordance redefined with the ratio of the “minimum satisfying acceleration” (MSA) to the A_max of the car.

Method:

Two groups of nine drivers drove cars differing in their A_max. They were instructed to attempt overtaking maneuvers in 25 situations resulting from the combination of five MSA and five MSV values.

Results:

When overtaking frequency was expressed as a function of MSV and MSA, maneuvers were found to be initiated differently for the two groups. However, when expressed as a function of MSV/V_max and MSA/A_max, overtaking frequency was quite similar for both groups. Finally, a multiple regression coefficient analysis demonstrated that overtaking decisions are fully explained by a composite variable comprising MSA/A_max and the time required to reach MSV.

Conclusion:

Drivers reliably decide whether overtaking is safe (or not) by using low- and high-order variables taking into account their car’s maximum velocity and acceleration, respectively, as predicted by “affordance-based control” theory.

Application:

Potential applications include the design of overtaking assistance, which should exploit the MSA/A_max variables in order to suggest perceptually relevant overtaking solutions.