Driving performance metric definitions, calculations and criterion for error
| Driving performance metric | Definition of metric | Calculation | Source | Criterion for error in SDA |
|---|---|---|---|---|
| Operational manoeuvres | ||||
| Lane choice10 | Lane selection during turn at an intersection | Lane position up to 2 s prior to initiation of turn as indicated by a turn of the steering wheel beyond ±45° | Simulator | Controlled and uncontrolled left turns: turning left at intersection from the right lane |
| Lateral acceleration during turn11 | Lateral acceleration during a turn at an intersection | Lateral acceleration | Simulator | Controlled and uncontrolled left turns: lateral acceleration ≥0.5 g |
| Speed10 | Velocity | Velocity relative to posted speed limit | Simulator | Controlled left turns, rear-end and hidden hazard (car in driveway): velocity exceeds posted speed limit by 10% in clear conditions and 5% in rainy conditions. Curves: velocity exceeds posted speed limit at any point in the curve. Uncontrolled left turns: velocity exceeds posted speed limit at any point in the turn |
| Stopping behaviour at a stop sign10 | Velocity at a stop sign | Minimum velocity at stop sign | Simulator | Controlled left turns: failure to reach velocity of zero at a stop sign |
| Traffic check10 | Glance sequence at intersection | Video coder identified glance location sequence | Eye tracking data-video | Controlled left turns: failure to make a glance sequence of left-right-left within 5.5 m of intersection |
| Turn signal use10 | Application of turn signal to alert other road users of a turn | Activation of turn signal | Simulator | Controlled and uncontrolled left turns: failure to use turn signal |
| Yaw11 | Vehicle heading correction after completion of a turn at an intersection | Vehicle heading correction after completion of turn as indicated by the return of the steering wheel to 0° | Simulator | Controlled and uncontrolled left turns: vehicle heading correction is altered by more than ±6° after turn completion |
| Advanced manoeuvres | ||||
| Braking behaviour in a hazardous situation11–13 16 | Instance of substantial longitudinal deceleration in response to a hazardous situation | Rear-end events: based on headway time and instance of longitudinal deceleration >0.6 g prior to a collision. Hidden hazard (car in driveway): based on velocity and instance of longitudinal deceleration >0.6 g prior to a collision | Simulator | Rear-end: headway time <3 s and no instance of longitudinal deceleration >0.6 g Hidden hazard (car in driveway): Velocity exceeds posted speed limit by 5% and no instance of longitudinal deceleration >0.6 g |
| Excess glance duration >1.5 s14 | Summed glance duration off forward roadway over 1.5 s | Time duration between when the cross-hairs of the ASL eye-tracker left the area of the centre display view and reappeared during a distraction task: duration of glances were summed | Eye tracking data video | Rear-end with distraction: glance duration off forward roadway >1.5 s |
| Gap selection17 | Choice of time to enter an intersection and proximity to other vehicle in intersection | Video coding determined if participant waited for cross traffic. For participants who did not wait, postencroachment time (PET) was calculated | Simulator (video and data) | Controlled left turns: PET <1.5 s. Participants who waited for cross traffic did not receive an error |
| Headway time16 | Instantaneous time to reach lead vehicle | Distance/velocity of participant vehicle centre of gravity to lead vehicle centre of gravity. Video coder estimated distance for a minority of participant scenarios where vehicle information was not available* | Simulator | Rear-end: distance/velocity of participant vehicle to lead vehicle <3 s |
| Scan left for intersection15 | Glance to the left as participant approaches an intersection | Video coder identified glances to left as participant approached intersection: coded from the location of instructions to make a left turn until ∼5.5 m from intersection | Eye tracking data video | Controlled and uncontrolled left turns: no recorded glances to left as participant approached intersection |
| Scan right for intersection15 | Glance to the right as participant approaches an intersection | Video coder identified glances to right as participant approached intersection: coded from the location of instructions to make a left turn until ∼5.5 m from intersection | Eye tracking data video | Controlled and uncontrolled left turns: no recorded glances to right as participant approached intersection |
| Scan right for hidden hazard15 | Glance to the right as participant approaches a hidden hazard | Video coder identified glances on fence, driveway and car as participant approached hazard event and record time stamps of glances and when car pulls out | Eye tracking data video | Hidden hazard (car in driveway): no recorded glances to right as participant approached hidden hazard event |
*Video coding calculation of headway time to known simulator derived values of headway time and found that the mean difference between both samples was 0.13 s (95% CI 0.01 to 0.27).
SDA, Simulated Driving Assessment.