- April 11, 2024
- Perspectives
America’s Untapped Transportation Potential: School Bus Traffic Signal Prioritization
Michael Ruelle, P.E.
Transportation Engineer
- Improve safety for drivers and students.
- Decrease route travel times
- Increase service reliability
- Reduce bus operations and maintenance costs
- Lower emissions
- Address the shortage of school bus drivers
Measuring the Effectiveness of Connected Vehicle Technology
To demonstrate the technology, wireless connected vehicle (CV) hardware was installed on two Fulton County school buses, one running on diesel fuel and one running on propane. The two school buses began and ended their daily routes at the North Fulton Transportation Center and drove routes serving three schools. Wireless CV hardware was also installed on 62 traffic signals in their routes.
Each bus sent GPS-based location information to cloud-hosted CV software. That software, when observed near a traffic signal, would request priority service in the traffic signal for the approaching school bus. The signal would then turn green early or extend a green light so the approaching school bus could proceed through the intersection without stopping.
Kimley-Horn conducted a before-and-after analysis of the school bus priority solution to quantify its benefits. The before period occurred over four weeks in April, followed by the after period over four weeks in May.
Time, Efficiency, and Sustainability Benefits of School Bus Signal Prioritization
The team analyzed five primary performance metrics—travel time, speed, number of stops, fuel consumption, and emissions. The results gathered from this study showed dramatic benefits.
Table 1: Average Improvement
| Travel Time | Average Speed | # of Traffic Signal Stops | |
|---|---|---|---|
Diesel Bus |
-12.4% |
14.2% |
-40.2% |
Propane Bus |
-14.0% |
20.5% |
-40.5% |
Overall |
-13.3% |
18.0% |
-40.4% |
Table 2: Average Reduction
| Fuel Consumption | Emissions | |
|---|---|---|
Diesel Bus |
-13.4% |
-12.4% |
Propane Bus |
-14.0% |
20.5% |
Overall |
-10.1% |
-9.9% |
The results from Table 1 highlight a substantial overall improvement in the reliability (and reduction in variability) of bus routes and better on-time performance. In other words, not only did buses arrive at their destinations on time more often, but they also arrived within smaller time windows, making service more predictable during the entire route. Table 2 results show cost and environmental benefits, which improve air quality and help create healthier and more livable communities.
In addition to quantitative performance metrics, the team interviewed each school bus driver to obtain qualitative feedback. Both drivers said they arrived early and/or on-schedule much more frequently than they did before the routes used traffic signal prioritization. The drivers also noted that their better on-time performance reduced their stress and allowed them to monitor student behavior more closely throughout the route. Drivers observed that fewer unscheduled stops reduced opportunities for students to stand up and exhibit unsafe behaviors, improving safety for everyone.
Optimizing School Bus Routes Could Boost Grades and Cut Costs
By getting students to school on time more reliably, the technology also provided the benefit of dropping off students at school earlier. Therefore, students could take advantage of the school’s free breakfast program. Research has shown that children who eat breakfast before standardized tests have significantly higher scores in math, spelling, and reading than those who don’t.
On the vehicle side, Fulton County Schools operate approximately 940 school buses that transport over 78,000 students per day and travel over 1,000,000 miles per month. Across the US, nearly 500,000 school buses transport more than 20 million students each day, and 95% of them run on diesel. The potential benefits of traffic signal prioritization scaled from two buses to thousands would cut fuel costs and reduce wear and tear, and therefore maintenance costs for participating cities and districts.
Furthermore, transportation planners could increase the number of average stops per route due to time savings—and still get students to school on time. This would reduce the number of routes, buses, and school bus drivers, improving everything from traffic congestion to the challenge of hiring enough school bus drivers. Nationwide, a 2023 study showed that 92% of school officials reported a shortage in bus drivers—an increase from 88% in 2022.
Connected Vehicle Hardware vs. Software
The school bus priority solution in this study was largely hardware-based. However, connected vehicle hardware can cost up to $10,000 per traffic signal and $5,000 per vehicle, negating many savings. A software-only solution provides similar functionality by working with an agency’s existing traffic signal infrastructure and their automated vehicle location (AVL) software.
This eliminates additional hardware at each traffic signal and does not require any on the vehicle. Software, therefore, enables traffic signal priority and preemption for any agency vehicle—including transit, emergency, freight trucks, and snowplows—at a much lower cost. It also removes significant and perpetual maintenance costs that come with hardware.
School bus signal priority technology can unlock savings year after year for school districts and municipalities. The savings span money, time, and emissions, which together can improve academic performance, budgets, staff shortages, and communities’ quality of life.
About the Author
Michael Ruelle, P.E.
Michael has more than 22 years of experience providing engineering and consulting services with a focus on ITS. Throughout his career, Michael has assisted both large and small public-sector clients across the country in managing their ITS assets, traffic signals, central software applications, and the communications networks that support them. His experience spans the entire ITS project life cycle, including planning, design, procurement, integration, operations, maintenance, and ultimately retirement and/or replacement. Michael also specializes in strategic planning for ITS, overall process improvement, configuration management, and project coordination across multiple disciplines and stakeholders.