Driving Simulation Study on V2I Technologies Found Audio Warnings Effective in Reducing Driver Speed by Approximately 11.4 Percent.

National Survey and Simulator Experiment Evaluate Driver Reactions and Safety Impacts of Audio-Visual V2I Advisory Systems.

Date Posted

Studying the impacts of Vehicle-to-Infrastructure (V2I) technologies on drivers’ behaviors and traffic safety

Summary Information

Connected vehicle technologies, especially Vehicle-to-Infrastructure (V2I) technologies, offer opportunities to enhance traffic operations, road safety and reduce traffic emissions and fuel consumption. This study examined the impact of V2I technologies on drivers’ behavior and traffic safety as well as drivers’ preferences, opinions and needs toward these V2I technologies. A driving simulator experiment was conducted with 42 drivers from Louisiana from different age groups. For the simulator experiment, drivers’ reaction and response towards heavy rain warning through an audio warning, an in-vehicle screen warning and Dynamic Message Signs (DMS) were evaluated. Additionally, a national survey study with 1571 responses was carried out to investigate drivers’ opinion, preference and needs towards V2I advisories for work zone warning, curve speed warning, emergency vehicle warning, train approaching warning, and adverse weather warning.


In this study, four specific scenarios were tested in driver simulation: (i) BASE: Heavy rain without warning, (ii) AUDIO: Heavy rain with in-vehicle audio warning, (iii) SCREEN: Heavy rain with in-vehicle screen warning, and iv) DMS: Heavy rain with DMS. The length of the simulated roadway network was eight miles, consisting of on-ramp, off-ramp and straight two-lane divided highway segments. The total experiment time was approximately 20 minutes. Speed change after the warning, response speed after warning, adopted speed during the rain, maximum acceleration and deceleration were used as performance measures.


  • Driving simulation found that the AUDIO scenario was effective in reducing average adopted driver speed by approximately 11.4 percent compared to BASE scenario (from 43.59 to 38.62 mph), while SCREEN only showed a minor improvement as compared to BASE scenario by reducing average adopted speed from 43.59 to 43.18 mph.
  • Driver simulation revealed an average compliance rate of 54 percent across the three scenarios, with heavy rain warnings and audio warning turning out to be effective in reducing the speed during heavy rain.
  • In terms of average acceleration rates, the driving simulator experiments revealed a 63 percent reduction (from 0.027 fts-2 to 0.010 fts-2) comparing AUDIO and BASE scenarios; a 51.9 percent reduction (from 0.027 fts-2 to 0.013 fts-2) comparing SCREEN and BASE scenarios; and a 44.4 percent reduction (from 0.027 fts-2 to 0.015 fts-2) comparing DMS to the BASE scenario.
  • Analysis of the survey responses revealed that around 85 percent of the respondents found V2I advisories would either be important or extremely important to increase their safety while driving.
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