Introduction
C-ITS systems that warn the motorcycle rider of an upcoming danger only work if the rider is interpreting the warning correctly and reacts accordingly. So far however, there is little knowledge about how long a rider reaction towards a warning takes.
Additionally, the question arises whether reactions from the passenger car domain can be applied to PTWs.
The following whitepapers describe two dynamic motorcycle riding simulator studies by CMC, which investigated motorcycle riders’ reaction times towards different types of warnings. Such knowledge can bridge the gap between results from the accidentology side to the use case and test case specific strategies. The latter focus on the decision on how an application’s display/ alert principle should be designed (e.g., advisory notification, crash warning, active intervention).
Additionally, the question arises whether reactions from the passenger car domain can be applied to PTWs.
The following whitepapers describe two dynamic motorcycle riding simulator studies by CMC, which investigated motorcycle riders’ reaction times towards different types of warnings. Such knowledge can bridge the gap between results from the accidentology side to the use case and test case specific strategies. The latter focus on the decision on how an application’s display/ alert principle should be designed (e.g., advisory notification, crash warning, active intervention).
What has been investigated
CMC has published three subsequent whitepapers regarding Rider Reaction Time based on a dynamic motorcycle riding simulator study.
The RRT I whitepaper dates from 2022 and remains available on this page for reference.
The RRT II whitepaper was written by the end of 2023 as an extension to RRT I, so that it contains all information on both studies.
The RRT III whitepaper, published in spring 2025, builds on the earlier findings and investigates the effects of different warning timings.
In RRT I, the focus was on the effect of a generic visual warning in the dashboard.
In RRT II, other types of warnings were included:
In both RRT I and RRT II, reactions in an urban and a rural scenario were tested. These did not include imminent crash warnings, but advisory warnings with 3 seconds between warning onset and the potentially critical situation becoming visible. A baseline measurement was included which investigated rider responses in the same scenarios without any warning.
These studies are a first step towards empirical evidence in this domain.
The RRT I whitepaper dates from 2022 and remains available on this page for reference.
The RRT II whitepaper was written by the end of 2023 as an extension to RRT I, so that it contains all information on both studies.
The RRT III whitepaper, published in spring 2025, builds on the earlier findings and investigates the effects of different warning timings.
In RRT I, the focus was on the effect of a generic visual warning in the dashboard.
In RRT II, other types of warnings were included:
- Visual: mirror-mounted LEDs
- Visual: Head-Up Display
- Auditory: warning tone
- Haptic: vibration pattern of a wrist band
In both RRT I and RRT II, reactions in an urban and a rural scenario were tested. These did not include imminent crash warnings, but advisory warnings with 3 seconds between warning onset and the potentially critical situation becoming visible. A baseline measurement was included which investigated rider responses in the same scenarios without any warning.
These studies are a first step towards empirical evidence in this domain.
Important outcomes
RRT I:
- In 16.7% of cases, the purely visual dashboard warning was not recognized at all.
- Among the other cases, the average time between onset of the notification and gaze towards the dashboard was already about 1 second.
- The average time between notification onset and ‘throttle off’ was about 2 seconds.
- The average time between notification onset and ‘initiate braking’ was about 2.5 seconds.
- The mentioned reaction times were shorter in the urban scenario compared to the rural one, in which the situation was perceived as less critical.
- All four investigated warning types were superior to the baseline condition.
- Mirror-mounted LEDs and the haptic bracelet had no missed warnings at all.
- PTW-fixed devices such as the mirror-mounted LEDs had the highest acceptance due to reasons of comfort (no additional device to take care of) and safety (no stable connection between PTW and external device necessary).
- The primarily reported response across all types of warnings was an attention allocation to the forward roadway.
- The earlier attention allocation allows for less respectively later decelerations.
Other findings from RRT I and RRT II
Another interesting observation could be that, in the more time-critical urban scenario, all riders who had seen the warning, initiated braking before the obstacle became visible. In combination with the favourable evaluation of the test riders after the experiment, this shows a good potential for the safety benefit of C-ITS applications.
In comparison to driver reaction times in passenger car studies, more missed warnings were observed for some of the warning types, reaction times seem longer and reaction time distributions seem wider; hence there is a clear need for PTW-specific reaction time studies.
Furthermore, RRT II showed the potential of different types of warnings in terms of rider reactions as well as subjective measures such as acceptance. These studies’ results can contribute to rider safety e.g., by means of an improved understanding of user requirements regarding different types of warnings and regarding the timing of notifications; Additionally, by means of delivering valuable input to rider behaviour models in the context of simulation.
In comparison to driver reaction times in passenger car studies, more missed warnings were observed for some of the warning types, reaction times seem longer and reaction time distributions seem wider; hence there is a clear need for PTW-specific reaction time studies.
Furthermore, RRT II showed the potential of different types of warnings in terms of rider reactions as well as subjective measures such as acceptance. These studies’ results can contribute to rider safety e.g., by means of an improved understanding of user requirements regarding different types of warnings and regarding the timing of notifications; Additionally, by means of delivering valuable input to rider behaviour models in the context of simulation.
Design of RRT III
The focus of this report is on investigating rider responses to different warning timings. Warnings that are too early may be perceived as unnecessary or false positive warnings, decreasing trust in the system. Warnings that are too late may result in delayed responses, missed warnings, false negatives, or even crashes.
The warning timing was varied in four levels based on the real-time calculated Time-to-Collision (TTC), by a TTC of 1.7 vs. 2.2 vs. 2.7 vs. 3.2 seconds. Two rural test scenarios were applied. Mirror-mounted LEDs provided an imminent visual crash warning to the rider by flashing for 3 seconds in the colour red.
The warning timing was varied in four levels based on the real-time calculated Time-to-Collision (TTC), by a TTC of 1.7 vs. 2.2 vs. 2.7 vs. 3.2 seconds. Two rural test scenarios were applied. Mirror-mounted LEDs provided an imminent visual crash warning to the rider by flashing for 3 seconds in the colour red.
Important outcomes of RRT III
- No missed warnings were observed.
- On average, throttle-off responses were observed 0.7-1.0 seconds after the warning onset, braking responses were observed 0.8-1.1 seconds after the warning onset.
- Across different levels of warning timing, these reaction times were comparable.
- As a result, the time remaining between deceleration and potential hazard increased with earlier warning timing.
- For the given scenario, significant safety benefits in terms of decreased situation criticality were measured for any of the four levels of warning timing between TTC = 1.7 s and TTC = 3.2 s.
- The design of the warning as ‘imminent crash warning’, in comparison to the advisory-style notification in the earlier RRT studies, appears to have shortened the rider reaction times to a level that is more comparable to car driver reactions from studies/guidelines in the automotive field.
- The warning at TTC = 1.7 s was given at about the same time as the potential hazard was becoming visible on the road ahead. Consequently, the 1.7 s warning did not provide any safety benefit in terms of reaction time. Still, the 1.7 s warning increased perceived safety and acceptance of the system by the riders. Moreover, even this late warning would still be beneficial if the riders were distracted and did not recognise the potential threat themselves.
Documentation
RRT III: Scroll through the complete document here below, or download it as PDF: