"Intersection Crossing" Project (2011 – Present)

Acronym:  Intersection Crossing

Name: Competition between affordances while approaching an intersection

Type: Fundamental reseach

Funds: Doctoral fellowship (Contrat Doctoral, Ministère de l’Éducation Nationale de la Recherche et de Technologie)

key researchers: Antoine MORICE, Geoffrey MARTI, Gilles MONTAGNE

Collaborators: -


The project :

The "Intersection Crossing" project aims at studying how braking and accelerative actions are coordinated at the approach of an intersection.

Theory :

Driving a car is a typical situation in which an agent has to choose the most suitable maneuver to perform from multiple alternatives. Indeed, a safe approach to an intersection implies that drivers can simultaneously manage two scenarios: they either choose to cross or to give way to an oncoming vehicle. Gibson and Crooks (1938) proposed a theoretical framework capable of explaining driver's behavior in such a situation. In this seminal paper, they defined two major concepts: the Field of Safe Travel (FST) defined as the “field of possible paths which the car may take unimpeded” (p. 454), and the Minimum Stopping Zone (MSZ) defined as the “zone within which our driver could stop if he had to” (p. 457). Safe driving behavior was hypothesized to be the driver's response to the simultaneous perception of the boundaries of these two spatiotemporal regions, which would specify the driver's current crossing and stopping possibilities. Gibson and Crooks proposed that stopping-ability depends on the relation between FST and MSZ. They suggested that such an affordance can be formalized as the ratio between the FST and the MSZ. 


Participant sat in a fixed-base simulator (Mobsim, France) in front of a large screen onto which a virtual scene was rear-projected by a video projector (Barco iQ R500) at a frame rate of 60 Hz. Their action of their right foot on the brake and accelerator pedals and their manipulation of the steering wheel (ECCI Trackstar 6000 GTS) were monitored via a USB signal sent to a computer that hosted a customized OpenGL virtual reality software that in turn updated the virtual scene.

From the participant's viewpoint, the visual scene was composed of an intersection formed by two straight, orthogonal roads, bordered by trees. An oncoming vehicle approached the intersection on this road.


Intersection-Crossing Setup

Past Experiments :

Experiment #1 : First investigation of the role of CTcross and CTstop in decision making

Three groups of participants drove cars with identical acceleration capabilities but different braking capabilities and were asked to try to cross an intersection before an oncoming car traveling orthogonally blocked the route, if they deemed the maneuver to be safe. Alternatively, they could decide to stop before the intersection to let the oncoming car cross. Finally, as a last resort, they could decide to exit on the roadside. The intersections were identical among groups.

Results showed that although the crossing possibilities (CTcross) were the same for all groups, there were between-group differences in crossing frequency. This suggests that stopping possibilities (CTstop) play a role in the driver's decision-making process, in addition to the crossing possibilities. These results can be accounted for by a behavioral model of decision making, and provide support for the hypothesis of choice between affordances.







Key references (downloadable version in page Publications) :

  1. Marti, G., Morice, A.H.P. & Montagne, G. (2015) Drivers’ decision-making when attempting to cross an intersection results from competition betwwen affordances, Frontiers in Human Neurosciences, 8:1026. doi: 10.3389/fnhum.2014.01026

 "Overtaking" Project (2008 – present)

Acronym:  "Overtaking"

Name: Overtaking while driving

Type: Fundamental research

Funds: Doctoral fellowship (Contrat Doctoral, Ministère de l'Education Nationale de la Recherche et de Technologie), Lab's fund (Action Concertée Incitative, Institute of Movement Science Etienne-Jules Marey funds)

key researchers: Antoine MORICE, Numa BASILIO, Gilles MONTAGNE

Collaborators: Gabriel DIAZ, Brett J. FAJEN

The project :

The "Overtaking" project aims at studying how overtaking maneuvers are initiated and regulated.

Theory :

Traditionally, perceptual processes leading to the selection of suited action mode can be studied through the affordance theory (Gibson, 1977, Warren, Jr., 1984; Warren, Jr. & Whang, 1987) whereas action should be regulated by “laws of control” (Warren, 1988). However, the “affordance-based control” framework (Fajen, 2007) challenge this view and suggests that affordances are perceived not only before the action, but also throughout it, to regulate action. We hypothesized that drivers could perceive possibilities for overtaking offered by the driving situation by perceiving an affordance for ‘passability’ and regulate their behavior accordingly. This ‘passability’ affordance could be embodied in the relationship between different action capabilities related to the vehicle driven (e.g., the Maximal Velocity VMAX and Maximal Acceleration AMAX of the car) and the kinematics constraints of the driving situation experienced (e.g., the Minimum Satisfying Velocity MSV and/or Acceleration for successful overtake MSA).

Setup :

We use a fixed-base simulator (Mobsim, France) supporting  spring-loaded pedals (Trackstar 6000 GTS, Extreme Competition Controls Inc., Minneapolis/Burnsville, MN, USA) and a steering wheel (Trackstar 6000 GTS, Extreme Competition Controls Inc., Minneapolis/Burnsville, MN, USA). From the USB signals of pedals and steering wheel, a custom-made virtual reality application (ICE software) running on a host computer PC compute on-line the virtual scene that is stereoscopically displayed at a frame rate of 75 Hz in a head-mounted display (Hi-res 900 stereo, Cybermind corp., Maastricht, The Netherlands). An integrated electromagnetic head tracking system (6 DoF Flock of Birds, Ascension Technology Corp., Milton, VT, USA) link the viewpoint in the virtual world with rotations of the head.

Setup screenshot

Past Experiments :


Experiment #1 : First definition f the overtaking ability affordance involving velocities

In the first experiment, we defined the overtake-ability affordance as a ratio of the minimum satisfying velocity required for safe overtaking (MSV) to the maximum velocity of the driver’s car (Vmax). Two groups of participants performed overtaking maneuvers, if deemed possible, by driving either a slow (Vmax = 25 m/s) or a fast (Vmax = 32.5 m/s) virtual car in overtaking situations constrained by 14 values of MSV. As shown on the figure, for any given MSV condition, participants in the fast car group were more likely to attempt an overtaking maneuver. However, when MSV was expressed in intrinsic units as a ratio of Vmax for both groups, the frequency of overtaking was not significantly different across groups. Furthermore, overtaking frequency dropped to near 0% for both groups when MSV exceeded Vmax. In accordance with the affordance-based framework (Fajen, 2007), our results suggest that participants select their 30 overtaking maneuvers by perceiving an overtake-ability affordance.



Experiment #2 : Second definition of the overtaking ability affordance including accelerations

In the second experiment, we defined the vertake-ability affordance as the ratio of the “minimum satisfying acceleration” (MSA) to the maximum acceleration of the driver's car (Amax). Two  groups  of  nine  drivers  drove  cars differing in their Amax. They were instructed to attempt overtaking  maneuvers  in  25  situations  resulting  from the combination of five MSA and five MSV values. We evidenced that 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/Vmax and MSA/Amax, 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/Amax and the time required to reach MSV. Drivers were thus found to 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.



Key references (downloadable version in page Publications)

  1.  Morice, A.H.P., Diaz, G.J., Fajen, B.R., Basilio, N., Montagne, G. (2015) An affordance-based approach to visually guided overtaking, Ecological Psychology, 27(1), 1-25
  2. Basilio N., Morice, A.H.P., Marti, G., Montagne, G. (2015) High and low order overtaking-ability affordances: Drivers rely on the maximum velocity and acceleration of their cars to perform overtaking maneuvers. Human Factors: The Journal of the Human Factors and Ergonomics Society,57 (5), 879-894