Grade separation
- Description
- Notable Practices
- Images and Audio
- References
The “grade” of a highway-rail crossing refers to its elevation. When the roadway and railroad tracks both exist at the same elevation they are considered “at grade”. Separating the grade, by constructing an underpass or overpass, can provide safe passage from one side of the railroad tracks to the other for pedestrians and/or vehicles. Grade-separated crossings are expensive to build and may be underutilized if not properly designed.
The American Association of State Highway and Transportation Officials (AASHTO) guide for the planning, design, and operation of pedestrian facilities indicates that grade-separated crossings should consider the following guidelines [1]:
- Ensure that the crossing structure is accessible to all users and with adequate width for the safety of anticipated pedestrian volumes.
- Use barriers/railings to provide additional security to pedestrians.
- Ensure that the crossing is well lit.
Grade separation may be considered when there is a location with an incentive for pedestrians to cross the tracks, such as a shortcut between a residential area on one side and a pedestrian attraction (parking lot, shopping center, schools, parks, etc.) on the other. Locations where at-grade crossings are frequently blocked by train activity may also increase the risk of unsafe pedestrian behaviors, such as passing between the cars of a stopped train. Though, if the grade separated path is inconvenient or takes too long to navigate, it may not be used by pedestrians, even if the new path is safer [2]. Further, grade-separated crossings can be expensive and take a long time to design and build. Thoughtful community planning is essential to ensure resources allocated to constructing grade-separated crossings are worth the cost.
One study evaluated the effects of closing and replacing a grade crossing with a vehicular and pedestrian overpass bridge and found mixed results. The number of trespassers who entered the right-of-way in that area increased overall. However, the number who trespassed while a train blocked the crossing, a frequent challenge in this location, decreased significantly, as did the number of train strikes at this location [2]. Another study showed the proportion of pedestrians who used an overpass bridge to cross the tracks increased substantially immediately after education and environmental interventions, highlighting the potential value of pairing the engineering solutions with community education [4].
Additional search terms: overpass, underpass- If the grade separation is constructed to provide access after closing an existing at-grade crossing, ensure that the crossing is properly closed by restricting access to railroad right-of-way by installing fencing. See Right-of-way fencing [1].
- Prioritize providing access to pedestrians at locations with frequently blocked crossings [2].
- Grade separation may be most beneficial where trespassing is high—perhaps because, residential neighborhoods are separated from community resources by the railroad tracks—or there are unacceptable traffic delays due to stopped trains.
- Grade separation works best when combined with other prevention measures; some examples include Trespassing signage, Suicide prevention messaging, Railroad safety messaging, Community stakeholder collaboration, and Safety patrols and law enforcement.
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[1] American Association of State Highway and Transportation Officials. (2004). Guide for the Planning, Design, and Operation of Pedestrian Facilities. The American Association of State Highway and Transportation Officials.
Document Excerpt: The purpose of this guide is to provide guidance on the planning, design, and operation of pedestrian facilities along streets and highways. Specifically, the guide focuses on identifying effective measures for accommodating pedestrians on public rights-of-way. Appropriate methods for accommodating pedestrians, which vary among roadway and facility types, are described in this guide. The primary audiences for this manual are planners, roadway designers, and transportation engineers, whether at the state or local level, the majority of whom make decisions on a daily basis that affect pedestrians. This guide also recognizes the profound effect that land use planning and site design have on pedestrian mobility and addresses these topics as well. [see Section 4.4 Maintenance of Pedestrian Traffic in Construction Work Zones for relevant information].
[2] Ngamdung, T. (2019). Effect of Grade Separation on Pedestrian Railroad Trespass Activity at Shuttlesworth Drive in Collegeville, AL. Technical Report No. DOT/FRA/ORD-19/11. Washington, DC: U.S. Department of Transportation, Federal Railroad Administration.
Abstract: The Volpe Center, under the direction of FRA’s Office of Research, Development, and Technology, conducted a research study to evaluate the effects of closing and replacing the Fred L. Shuttlesworth Drive grade crossing (Crossing ID 352514C) with a vehicular and pedestrian overpass bridge on trespassing along a rail corridor in Birmingham, AL. Trespassing events were coded for 10 hours per day for 5 weekdays before construction of the overpass bridge and then again for approximately 5 months after the opening of the overpass bridge.
Results indicate that the rate of trespassers increased by 72 percent, from 44.74 to 76.91 per 100 pedestrians entering the railroad right-of-way, after the construction of the overpass bridge. However, high-risk trespass activities (trespassing during train events and trespassers physically interacting with a train) decreased significantly after the construction of the overpass bridge. Trespassing during train events decreased by 84.3 percent, from 7.05 to 1.10 trespassers per train event, and trespassers physically interacting with a train decreased by 92.6 percent, from 1.62 to 0.12 trespassers per train event after the construction of the overpass bridge.
[3] Lobb, B., Harré, N., and Suddendorf, T. (2001) An evaluation of a suburban railway pedestrian crossing safety programme. Accident Analysis & Prevention. 33(2) 157-165.
Abstract: This study evaluated a programme of educational and environmental (access prevention) interventions designed to reduce the incidence of illegal and unsafe crossing of the rail corridor at a suburban station in Auckland, New Zealand. Immediately after the programme of interventions, the proportion of those crossing the rail corridor by walking across the tracks directly rather than using the nearby overbridge had decreased substantially. Three months later, the decrease was even greater. However, the educational and environmental interventions were introduced simultaneously so that the effects of each could not be separated; nor could other unmeasured factors be ruled out. Anonymous surveys administered immediately before and 3 months after the interventions indicated that while awareness of the illegality of walking across the tracks had increased slightly, perception of risk had not changed. This suggests that the educational interventions may have had less effect than the access prevention measures.
Toole, J. (2010). Update of the AASHTO Guide for the Planning, Design, and Operation of Pedestrian Facilities, National Cooperative Highway Research Program (NCHRP) Project 20-07.
Description: This document provides and literature review and survey results regarding how to improve the previous version of the AASHTO Pedestrian Guide.