Driving Simulator Study with 50 Drivers Evaluating the Effectiveness of Warning Messages for Work Zones Finds Energy and Environment Benefits.
Nationwide, United States
Assessment of In-Vehicle Messages in the Advance Warning Area of a Work Zone
Summary Information
Connected vehicle technologies are known to not only enhance the mobility and safety of traffic operations, but also potentially reduce fuel consumption and exhaust emissions. In work zones, for example, with the help of both the audio and image based in-vehicle messages, drivers can be provided with early warnings about the road conditions via various communication methods. This study tested, developed, and compared an in-vehicle warning system to prevent occurrence of work zone crashes and reduce vehicle emission using data from driving simulations conducted in June 2017 with a simulated work zone.
METHODOLOGY
This study tested three scenarios: (i) work zone with no audio or image warning system (NO MESSAGE), (ii) work zone with a voice warning system (VOICE MESSAGES), and (iii) work zone with a mixed warning system of audio and image (MIXED MESSAGES). A total of 50 drivers were recruited in the United States holding a valid drivers’ license, for the driving simulation tests conducted under test and control scenarios. During the formal driving test, each participant was requested to drive through a work zone area to experience no or pre-set in-vehicle warning messages for the work zone traffic control. After the driving test, the participants immediately proceeded with NASA Task Load Index (NASA-TLX) survey.
Speed and acceleration were selected as performance measures for the evaluation matrix. Using the collected data, the study weighed and scored the performance measures in the evaluation matrix by assigning a score of ‘one’ to favorable scenarios, and zero otherwise. The total emissions from each scenario were estimated by the Environmental Protection Agency (EPA) software the Motor Vehicle Emission Simulator (MOVES), with vehicle speed, acceleration, and vehicle specific power (VSP) data. Vehicle emission factors of the three scenarios were estimated for CO2, CO, HC, and NOx emissions.
FINDINGS
- The results indicated a 16.4 percent reduction (from 0.61 g/m to 0.51 g/m) in CO2 emissions for MIXED MESSAGES scenario compared to NO MESSAGE scenario.
- Similarly, a 16.3 percent reduction (from 0.49 mg/m to 0.41 mg/m) in CO emissions was estimated for MIXED MESSAGES scenario compared to NO MESSAGE scenario. The same result was also found for HC emissions comparing the MIXED MESSAGES and NO MESSAGE scenarios.
- Regarding NOx emissions, a 19 percent reduction (from 2.21 mg/m to 1.79 mg/m) was estimated comparing the MIXED MESSAGES and NO MESSAGE scenarios.
- In the MIXED MESSAGES scenario, it was found that a higher percentage (42 percent) of speed fell within the range of “60-70” km per hour (37-43 miles per hour) where the speed limit was 72 km per hour (44.7 miles per hour), showing that the mixture of image and voice messages had great impact on the drivers’ speed compliance behavior.
