Driver Assist System Technology to Support Bus-on-Shoulder Operations
The Twin Cities Metropolitan area has an extensive network of bus-on-shoulder (BOS) operations, where bus operators use roadway shoulders at their discretion to bypass traffic congestion when speeds on general purpose lanes drop below 35 miles per hour.
This study introduced the Generation 2 (Gen2) Driver Assist System (DAS) used by the Minnesota Valley Transit Authority (MVTA) for BOS operations. The Gen2 DAS was a GPS-based technology suite, providing lane keeping information, lane departure warnings, and collision avoidance advisories to operators guiding their buses on the shoulders. It provides lane position feedback to the driver via light emitting diode (LED) warning lights embedded in the dashboard, warning icons on a liquid crystal display (LCD) touch screen, and a vibrating seat. The Gen2 DAS was installed on 11 buses that run on Cedar Avenue between Minneapolis and Northfield in Minnesota in March 2017.
An independent evaluation of the Gen2 DAS-equipped buses was conducted over 12 months, starting in March 2017 in five core areas, namely route system performance, customer satisfaction, bus operator satisfaction, maintenance, and safety. Route system performance was evaluated in terms of bus on-time performance, bus travel time, and distance traveled in the shoulder. Data from the buses’ automated vehicle location (AVL) system was used to calculate on-time performance and travel time. Customer satisfaction was measured by reviewing MVTA’s monthly customer complaint logs and tallying the number of complaints related to shoulder usage. Bus operator satisfaction was measured by conducting before-and-after surveys of the DAS-trained bus operators via in-person interviews. The “before” surveys were conducted in April 2016, immediately prior to DAS training with 37 participants, and the “after” surveys were conducted in February 2018, the last month of the evaluation with 17 participants. Bus maintenance was evaluated by examining the monthly maintenance logs and calculating the number of days each bus was out of service. Safety was measured in terms of accidents reported in the shoulder lane.
- In terms of route system performance, Gen 2 DAS buses demonstrated a slightly better (about 1.1 percent points, i.e. 88 percent versus 87 percent) on-time-performance on average in the AM period compared to the non-DAS buses.
- In terms of customer satisfaction, the number of complaints dropped from 12 to 4 per year (66 percent improvement) after the implementation of DAS.
- As far as the bus operator satisfaction is concerned before and after the DAS implementation, bus operators involved in the evaluation survey went from feeling confident to very confident about driving on the shoulder (mean score improved from 2.41 in the before survey to after mean score of 2.53). However, the mean score for stated level of stress worsened from 1.08 to 1.41, and the mean score for perceived safety worsened from 1.86 to 1.65.
- Based on the results of the data analysis, the DAS buses had better maintenance performance than the non-DAS buses with 37.5 percent less down time due to being out for maintenance (comparing 2.4 days a month for non-DAS buses to 1.5 days a month for DAS buses).
- There were zero accidents in the shoulder during both the baseline year and the implementation year. This applied not just to the DAS buses but to the entire MVTA fleet. Although there were no accidents with the DAS buses, there was one safety-related incident early in the evaluation.