Iowa Truck Parking Information and Management System (TPIMS) Evaluation Found HOS Violations Declined by 40.7 Percent After Deployment.
Evaluation of a Truck Parking Information System Deployment Using Parking Flow Data, Hours-of-Service Violations, and Driver Surveys from 2019 to 2021.
Iowa, United States
Evaluation of Iowa Truck Parking Information and Management System Phase 2: Performance Measures and Data Analysis
Summary Information
Commercial truck drivers often face challenges in finding available parking along major freight corridors. To address this issue, Iowa participated in the multi-state Truck Parking Information and Management System (TPIMS) project led by the Mid America Association of State Transportation Officials (MAASTO). TPIMS project was designed to monitor truck parking availability at public and private facilities and provide real-time information to drivers to help them make safer and more efficient parking decisions, along I-80, I-29, I-35, I-380, and I-235. The system went live in January 2019 and was disseminated to drivers through a statewide traveler information portal, smartphone applications, and in-cab information systems. This Phase 2 evaluation study examined system performance during the 2019-2021 grant period, focusing on utilization, reliability, and safety impacts.
METHODOLOGY
The evaluation used multiple data sources and performance measures to assess Iowa TPIMS utilization, reliability, and safety impacts. Data sources included (i) fine-grained parking flow records from in-ground puck sensors and in-and-out radar sensors, (ii) hours-of-service (HOS) violation records, (iii) TPIMS surveillance images, (iv) regional truck parking surveys conducted in 2016, 2018, 2020, 2021, and (v) a truck driver survey on system accuracy and usefulness. The performance measures used in this study included parking utilization rates, variation in utilization across sites, system downtime, data accuracy and reliability, HOS violations before and after deployment, parking demand cycles and low-availability periods, driver-reported parking search time, and driver perceptions of parking availability information. Anomaly detection and visualization methods were also used for better interpretation of system performance.
FINDINGS
- Iowa TPIMS improved truck parking utilization along I-80. After deployment, average parking utilization increased while the standard deviation across sites decreased, indicating that truck parking demand was distributed more evenly across the corridor. For example, across multiple sites, the average parking utilization at 2:00 a.m. (eastbound) increased from 71.57 percent in 2019 to 74.02 percent in 2020.
- HOS violations by corridor section declined during the three years following deployment, decreasing from 1.82 percent to 1.08 percent, a reduction of approximately 40.7 percent.
- Over the three-year grant period, 36 of 43 TPIMS sites, or approximately 84 percent, experienced system downtime of less than five percent, demonstrating high overall reliability of the system.
- TPIMS achieved comparable performance without roadside variable message signs, helping Iowa avoid VMS installation and maintenance costs while allowing TPIMS to be deployed at more sites than other participating states in the regional program.
