Prevention and Mitigation of Bridge and Tunnel Strikes (2025)
Chapter: 3 Data Needs and Sources
CHAPTER 3
Data Needs and Sources
Overview
Following the collapse of the Skagit River Bridge due to an overheight vehicle (OHV), the National Transportation Safety Board (NTSB) made several recommendations to prevent similar BrTS, such as the NTSB H-14-08 recommendation: “Develop a “Best Practices” guide that the states can use to prevent bridge strikes by overheight vehicles, including a framework for collecting bridge strike data and for ensuring communication of these data among the state agencies responsible for conducting bridge inspections and those responsible for issuing oversize load permits, to support the development of countermeasures.” The benefits of collecting bridge strike data and communicating that data to stakeholders are obvious: the data can be used to gain a better understanding of when, where, and why a bridge strike occurred. More importantly, the data can be used to develop operational changes, evaluate safety countermeasures, and determine cost-effective solutions.
Table 1 summarizes the data needed to analyze and model risks of BrTS collisions. State agencies may maintain their own information systems that contain detailed bridge information. The Moving Ahead for Progress in the 21st Century (MAP-21) legislation mandated the collection of element-level data on bridges (“[USC02] 23 USC 144: National Bridge and Tunnel Inventory and Inspection Standards” 2012). These element-level datasets include damage reporting.
Table 1. BrTS Data Needs and Sources
| Data Needs | Data Sources | Sample Data Elements |
|---|---|---|
| Bridge and tunnel inventory data | NBI, NTI, State DOT Highway Structure Information System (HSIS), and OSOW permitting systems | Bridge Identification Number (BIN), load design, maximum/minimum vertical clearance under, posted vertical clearance under, span, bridge width, superstructure design type, detour distance |
| Roadway inventory | State agencies following Model Inventory of Roadway Elements (MIRE) | Number of lanes, lane width, shoulder width, lateral clearance, necking (i.e., roadway approach width vs. curb-to-curb width), vertical/horizontal curve, lighting |
| Collision data | Crash data from state DOTs or highway safety agencies; and state bridge inspection data | Injury severity, bridge component hit, vehicle type, driver data, weather and pavement conditions. |
| Driver/carrier behavior data | FMCSA’s Safety Measurement System (SMS) | Driver and vehicle violations; crash reports; and investigation results |
| Traffic data | Highway Performance Monitoring System (HPMS) | Functional class, annual average daily traffic (AADT) (on/under), ADTT, posted speed limit |
| Weather | National weather services | Annual average rainfall, snowfall |
| Navigation (commercial) GPS data | Garmin or other devices, or popular apps used by commercial vehicle drivers | Structure clearances and load postings |
| Other | Light detection and ranging (lidar) data, Google Maps | Vertical clearance warning signs, rumble strips, roadside barrier systems, detailed bridge data |
While data collection on vertical clearance measurement and crashes for existing bridges follow well-established national guidelines, such as the FHWA Bridges and Structures Standards and Guidelines, the National Tunnel Inspection Standards, MMUCC, MIRE, and Best Practices in Permitting Oversize and Overweight Vehicles, few studies offer a comprehensive picture of data needs and data sources directly related to BrTS. Specifically, this chapter seeks to address the following questions:
- Can BrTS be identified from reportable motor vehicle crash data, and if so, can crash data document which part of the structure is struck so that a BrTS may be categorized by superstructure, substructure, and bridge rail/parapet?
- Can the bridges and tunnels crash data be linked with national structure databases (e.g., NBI, NTI)?
- Are any BrTS, other than reportable motor vehicle crashes, being regularly collected and archived by a public (e.g., state DOTs) or a private agency (e.g., insurance companies, motor carriers)?
- How is bridge vertical clearance data collected, archived, updated, and communicated among agencies who are responsible for bridge design, inspection, maintenance, OSOW permits, and bridge signing?
- Can any other data sources, such as weather, roadway and traffic conditions, driver characteristics and behavior, improve our understanding of the occurrence of a BrTS and its impact?
Search Methods for Data Sources
A literature review was conducted to understand commonly used data in the fields of BrTS research and practice (crash data, roadway, signage, and traffic data). The project team also conducted searches regarding the national/state-level bridge/tunnel inventory data maintained by FHWA and state DOTs (e.g., NBI, NTI, Wisconsin DOT (WisDOT) HSIS, and Indiana DOT (INDOT) Bridge Clearance Database), as well as automobile incident claim data maintained by private companies (e.g., Comprehensive Loss Underwriting Exchange (C.L.U.E.) Auto data).
Additionally, a search was conducted for all 50 states to garner information on how bridge clearance data are collected and managed. The goal was to find out which techniques are used for bridge vertical clearance measurement, which types of clearance data are collected, and the required data accuracy. This search also helped us understand the format of clearance databases, whether GIS capability is supported, how often the data is updated, and how the clearance data supports OSOW routing and permitting. Of particular interest were bridge inspection manuals and bridge inspection program coding guides published on state DOT websites, as well as any available clearance databases.
The project team also reached out to state DOTs (e.g., WisDOT, NYSDOT) and the motor carrier industry (e.g., Specialized Carriers & Rigging Association (SCRA), ProMiles) to aid the data collection and analysis efforts. This targeted outreach helped us understand the availability of data, issues and challenges related to the data, and general challenges related to BrTS.
Primary Data Needs and Data Sources
BrTS is a complex issue, one that is the result of several factors such as incomplete and inaccurate vertical clearance information and routing, inconsistent permit requirements, pilot car certification and escorting services, unsafe or inattentive driving behavior and OSOW permit compliance. To ensure the success of the project and to minimize data collection efforts, the project team focused on available data sources and also identified opportunities to leverage data collection efforts with existing or ongoing efforts by state DOTs and the motor carrier industry. This section presents information about data sources identified during the search and is organized into two subsections: 1) BrTS strike data and 2) bridge/tunnel vertical clearance data. The detailed review of the data needs and sources can be referred to Appendix B: Technical Memorandum: Data Needs and Sources.
