METHODOLOGY

VISSIM, a micro-simulation modeling tool, was used by researchers to evaluate the impact of TSP on bus travel time in Burlington, Vermont. The research assessed the impacts of transit priority on traffic on Route 15, which is a four-lane arterial connecting the suburbs to the city of Burlington, and on the Old North Route, which is a loop in the downtown area. The research compared bus travel time and delay per vehicle during operations without TSP (baseline condition) to operations with TSP. Performance measures are averages of the measures obtained over the course of multiple simulated runs. The simulations included baseline operations (i.e., without TSP) and two TSP scenarios, as summarized below.

Route 15

• Scenario 1 consisted of a 10 second green extension and 30 minute headway. Scenario 1 was run twenty times in VISSIM.
• Scenario 2 consisted of a 10 second green extension and 15 minute headway. The 15 minute headway was included to take into account stakeholders' interest in increasing the frequency of bus service in the downtown area. Scenario 2 was run eight times in VISSIM.

Old North Route

• Scenario 1: 10 second green extension with bus stops located on the nearside (i.e., before the intersection).
• Scenario 2: 10 second green extension with bus stops relocated from the nearside to the farside (i.e., the far side of the intersection)

FINDINGS
In general, the results show that TSP improved priority bus level of service without impacting other traffic.

Route 15 for Scenario 1 Performance

	Baseline	Scenario 1	Outcome
Bus Travel Time (sec)	828.44	790.35	5% reduction in travel time
Vehicle Travel Time	538.08	536.59	<0.5% reduction in vehicle travel time
Bus Delay	268.09	229.92	14.2% reduction in delay for priority buses
Vehicle Delay	304.08	300.64	1% reduction in delay for vehicles traveling in the same direction as priority buses
Bus Waiting Time - Inbound Buses	129.03	93.1	27.9% reduction in the rate of change in bus waiting time
Bus Waiting Time - Outbound Buses	31.55	35.45	12.4% increase in bus waiting time

Route 15 for Scenario 2 Performance

	Baseline	Scenario 2	Outcome
Bus Travel Time (sec)	836.76	788.49	6% reduction in travel time
Vehicle Travel Time	586.56	549.35	6% reduction in vehicle travel time
Bus Delay	295.61	246.73	16.5% reduction for delay for priority buses
Vehicle Delay	352.96	319.48	9.5% reduction in delay for vehicles traveling in the same direction as priority buses
Bus Waiting Time - Inbound Buses	121.22	88.13	27.3% reduction in the rate of change in bus waiting time
Bus Waiting Time - Outbound Buses	29.28	30.48	4% increase in bus waiting time

Old North Route for Scenarios 1 and 2 Performance

	Baseline	Scenario 1	Scenario 2	Outcome
Bus Travel Time (sec)	1420.3	1321.4	1285.9	Scenario 1 reduced travel time by 7% relative to Baseline. Scenario 2 reduced travel time by 2.5% relative to Scenario 1 (not statistically significant).
Total Vehicle Delay (hours) (Delay to Non-transit Vehicles)	79.61	80.09	80.68	Scenario 1 decreased vehicle delay by <1% relative to baseline (not statistically significant). Scenario 2 decreased vehicle delay by <1% relative to Scenario 1 (not statistically significant).

SUMMARY

TSP reduced average travel time for priority buses by 2.5 to 7 percent, reduced average delay for priority buses by 14.2 to 16.5 percent, reduced the average waiting time for priority buses by about 27 percent, and had a statistically non-significant impact on delay for other vehicles of less than 1 percent.

The findings indicate that TSP may increase transit bus level of service while also having a minimal impact on non-transit traffic. Considering that previous evaluations of TSP have found improvements in bus travel time, these findings are not entirely unexpected. However, the results are noteworthy because Burlington is smaller compared to other cities with TSP.