Affirmative street-crossing notifications were found to be more reliable and trusted than negative notifications in a sample set of older pedestrians.

University study compared s’ reactions to “safe to cross” or “not safe to cross” alerts, and found that the former were much more widely complied with.

Iowa City; Iowa; United States

Summary Information

Older pedestrians typically have more difficulty making road-crossing decisions than younger adults. An experiment conducted by researchers at the University of Iowa sponsored by the SAFER-SIM University Transportation Center sought to understand the implications of Vehicle-to-Pedestrian (V2P) communication to aid in this decision-making process. The researchers developed ability-based permissive alerts, indicating that it was safe to cross, and prohibitive warnings, indicating that it was not safe to cross, and deployed them in a virtual street-crossing environment. The experiment included 66 participants between the ages of 65 and 88.


The researchers found several key conclusions:
  • Participants who received permissive alerts were significantly more likely to cross the street when the gap in traffic was smaller than normal. Participants who received only prohibitive warnings did not differ in this aspect from participants who received no alerts whatsoever. This indicates that the permissive warnings are more likely to encourage more confidence in road-crossing ability.
  • Age was found to have a statistically significant impact on road-crossing time. Each 5-year increase of participant age corresponded with a 0.1 second increase in total road crossing time. The type of alerts that were received did not impact road crossing time.
  • Participants who received permissive alerts had 90 percent compliance with their notifications. There were some cases where participants were alerted that they had enough time to safely cross but chose not to. There were no cases where participants attempted to cross even when they had not received an affirmative alert that it was safe to do so.
  • Participants who received prohibitive warnings had only 73 percent compliance. Only one participant attempted to cross when they had received a warning urging them not to. However, there were many instances in which the warning turned off, indicating that it was safe to cross, yet the participant did not attempt to cross. This indicates that participants were more likely to make their own decisions about whether to cross or not.
  • Sixty-eight (68) percent of participants who received permissive alerts and fifty percent of participants who received prohibitive warnings described the notifications as making their decision-making easier.
  • Fifty (50) percent of participants who received permissive alerts and 55 percent of participants who received prohibitive warnings noted that they either ignored the notifications or preferred using their own judgement. However, many respondents indicated that they might be particularly useful in future contexts, such as when navigating an unfamiliar city or along a riskier stretch of road.
  • Forty-five (45) percent of prohibitive-warning recipients mentioned that the repeated warnings to not cross were annoying.

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Determining the Effect of Smartphone Alerts and Warnings on Older-Adult Street-Crossing Behavior

Author: Rector, K.; J. Kearney; and J. Plumert

Published By: SAFER-SIM University Transportation Center

Source Date: 03/01/2020



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Benefit ID: 2020-01459