Improving Safety at Rural Highway-Rail Grade Crossings by Utilizing Light Detection and Ranging (LiDAR) Technology

University  University of Nebraska-Lincoln (UNL)
Principal Investigators  Aemal Khattak, Ph.D., Civil Engineering (PI)
PI Contact Information  262D Whittier Research Center
P.O. Box 830851
Lincoln, NE 68583-0851
Office (402) 472-8126
Funding Source(s) and Amounts Provided (by each agency or organization)  Federal Funds (USDOT UTC Program): $75,284
Cost Share Funds (UNL): $37,642
Total Project Cost  $112,926
Agency ID or Contract Number  DTRT13-G-UTC59
Start and End Dates November 2013 — December 2015
Brief Description of Research Project  The objective of this research was to test and validate the feasibility of a computer- based tool that safety analysts can use to quickly assess rural highway-rail grade crossings for large truck traffic in case of an emergency or route closure situation. The suitability of many rural highway-rail grade crossings for use by large trucks with trailers is a concern because of the possibility of trucks getting stuck on the rail tracks when excessive grade difference exists between the rails and approach surface of the crossing highway. While trucks usually ply on designated routes, emergencies and highway closures may necessitate re- routing of trucks to rural highways with grade crossings that may not have the safe geometry needed for large trucks with trailers. Therefore, it would be useful to have a computer-based tool and relevant data by which analysts could quickly assess crossing suitability without the need for field visits. The availability of Light Detection and Ranging (LiDAR) data for most of NE makes it possible to develop a computer-based tool that allows analysts to assess the suitability of highway-rail crossings for large vehicles. LiDAR data are usually collected using an appropriately-equipped airplane that flies and collects the locations of millions of points on the Earth’s surface. Using geographic information systems (GIS) software, the point cloud can be converted into a terrain model replicating the surface profile. LiDAR data are available for most of Nebraska and in many cases free of cost. This research developed a computer-based tool utilizing LiDAR data that allows users to assess the suitability of rural highway-rail grade crossings for use by large trucks. Field validation of the results from the tool was carried out as part of this research.
Keywords highway-rail grade crossings, HRGC, rail grade, approach surface,  LiDAR, crossing geometry, GIS, terrain model, surface profile
Describe Implementation of Research Outcomes (or why not implemented) Place Any Photos Here Geo-referenced points of 160-ft ranges for crossing roads and a 2 meter resolution LiDAR elevation raster were integrated in the study area orthophoto using ArcGIS. An autonomous relative accuracy test of the data was conducted to see how accurately the data represented elevation of the study area. To conduct the assessment, LiDAR elevation data pertaining to the geo-referenced points in the three rail grade crossings were obtained from the GIS database and verified against field observations obtained using a geopositioning system and a theodolite. The two corresponding groups of data were compared for relative accuracy. Figure 1 shows the aerial photos of the rail grade crossing geometry and vertical elevation profiles between LiDAR data and field-measured data. The geo-referenced points were obtained along the arrows shown in the figure. In a range of 160-ft, point spacing for each was 2-ft resulting in 81 elevation points at each site. For the three sites, there were 243 elevation sample points for both LiDAR and field measured elevation data. A list of the total LiDAR and field elevation geo-referenced points appears in Appendix B. RMSE for each pair of all 243 points were only 0.30-ft, so the authors decided to proceed with further analysis.

All figures, pictures and tables can be accessed on Full Report link.
Impacts/Benefits of Implementation (actual, not anticipated) The objective of the research was to test and validate the feasibility of assessing humped highway-rail grade crossings for safe passage of vehicles with low ground clearance using LiDAR data. From amongst the selected design vehicles, the lowboy trailer was found susceptible to lodging at site 1 while the car carrier trailer was susceptible to lodging at sites 1 and 2. The passage of the other design vehicles (a rear-loaded garbage truck, two types of fire trucks, and a school bus) was not an issue at any of the three highway-rail grade crossing sites. Validation of the GIS-derived results in the field showed that all the identified blockage spots were correctly identified. The conclusion from the conducted research was that LiDAR data can be used for identifying potential hang-up issues at rail grade crossings.

This proposed method is efficient and safer because it avoids making measurements in the field where highway and train traffic may pose hazards to the safety of personnel. However, it is acknowledged that current updates to LiDAR data are infrequent and may not keep up with changes in the highway/rail networks. Therefore, any changes at or near highway-rail grade crossings after LiDAR data collection will likely require field assessment. This research only analyzed three highway-rail grade crossings; in future studies, more sites may be evaluated so the findings are more generalizable.

Moreover, work on this project has resulted in one paper presentation at the Transportation Research Board 96th Annual Meeting:
  • Kang, Y. and Khattak, A., “A Cluster-Based Approach to Analyze Crash Injury Severity at Highway-Rail Grade Crossings,” Proceedings of the Transportation Research Board 96th Annual Meeting, Washington, D.C., January 9, 2017.
Additionally, a detailed report that summarizes all the work performed under this project is made available and can be downloaded from the UTCRS website using the link provided below.
Full Report
Project Website