Driver warning systems are a tool in the pursuit of safer urban areas due to the high complexity of the environment, this may be even more of an issue for older drivers as they are over-represented in crashes. The aim of this driving simulator study was to determine whether a heads-up warning showing either a stop sign warning (SW) or caution sign warning (CW) 2.5 seconds prior to the anticipated crash would have a better effect on the driving performance of older drivers (compared to the control group) in scenarios of different criticalities.
Thirty-six older drivers (average age of 71.9, average 49.7 years driving experience) were divided into three groups: SW, CW, and a control. Each participant drove through four scenarios.
- Pedestrian 1 scenario: while turning a pedestrian crosses the vehicle’s path.
- Pedestrian 2 scenario: a pedestrian, obscured by parking cars, suddenly crosses the vehicle path.
- Vehicle scenario: lead vehicle comes to a sudden stop.
- Obstacle scenario: driver is confronted with a hay bale hidden behind a hill.
In each scenario the vehicle driven by the participant travels through a simulated urban road and has to make a turn when indicated by a voice output and an arrow in the speedometer. After the test drive, each subject was asked about the criticality and surprise of each scenario.
Driving data was logged by the simulation software. Participant’s subjective data was converted to a rating on a scale from 1 to 15.
Participants rated the Pedestrian 2 and Pedestrian 1 scenarios to be highly critical and highly surprising, revealing that the four implemented scenarios were of different criticalities.
The SW brake reaction time was the fastest in each scenario, followed by the CW. In the study, the SW had a positive effect on shortening the brake reaction time. Similar results are found when considering the maximum braking value. This variable was descriptively the highest to the SW, meaning that participants hit the brake pedal the hardest here compared to the CW and the control condition. Furthermore, the SW led to almost always the lowest mean velocity when reaching the maximum braking value.
The results of the study show that it is important to know what behavior a warning might trigger. In scenarios where the driver has to react immediately, the SW is best suited. But, if a sudden and firm brake reaction is not needed, as in the Vehicle and Obstacle scenario, the SW warning could have negative effects (e.g., high maximum braking value) and the CW is better suited.
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