Drivers showed a greater reduction in speed with presented with audible alerts and the overwhelming majority of participants understood the safety alerts used in the 500-participant Minnesota Road Fee Test study.
Minnesota, United States
Connected Vehicles for Safety, Mobility, and User Fees: Evaluation of the Minnesota Road Fee Test
Summary Information
In 2007, the Minnesota Legislature appropriated $5,000,000 for a technology research project exploring mileage based user fees (MBUF). The Minnesota Department of Transportation (Mn/DOT) was tasked with leading the effort of executing a pilot project to demonstrate technologies that would allow for the eventual replacement of the gas tax with a cost-neutral mileage charge.
The objective of the Minnesota Road Fee Test (MRFT) was to inform future public policy decisions regarding mileage-based user fees and connected vehicle applications. To accomplish this, Mn/DOT utilized a commercially available after-market device, a smartphone, to assess mileage-based user fees and convey safety alerts to drivers through in-vehicle signing.
Methodology
The in-vehicle safety alerts used two different kinds of alerts: visual and audible. Visual alerts showed the same traffic control device on the smartphone as appeared on the roadside (e.g., curve signage). Audible alerts worked by making the smartphone beep when the vehicle was traveling more than 5 mph over the posted speed limit for the area (e.g., school zones, speed zones). In this study there were a total of 98 signage zones, including school zones, speed zones, curves, and construction zones. Participants in the overall MBUF study were surveyed and interviewed regarding their experience with the visual and audible alert functions of the study smartphone device.
Benefits/Findings
Nearly all respondents who had seen the visual safety alerts reported they somewhat agreed or agreed that they knew why the alerts were displayed (97%), the alerts were easy to read (98%), and the alerts were easy to understand (99%).
The majority of respondents also somewhat agreed or agreed that they understood why the audible safety alerts occurred and that the audible safety alerts were easy to hear, with 95% of the experienced respondents responding this way to both statements.
Speed-related safety alerts were found to be effective at reducing speeds. Both visual and audible alerts appear to have improved speed limit compliance and reduced driver speeds, while drivers showed a greater reduction in speed when presented with audible alerts. The largest benefit was seen with the 7% of drivers who previously increased their speed upon entering the zone, but who slowed down upon entry when alerts were present. Overall there was an average reducing in speed of 9.0 mph among these drivers.
Both visual and audible alerts appear to have improved speed limit compliance and reduced driver speeds, with drivers showing a greater reduction in speed when presented with audible alerts. The most significant effect was among drivers who were previously increasing their speed upon entering the zone.
