Office of Planning, Environment, & Realty (HEP)

Rails-with-Trails: Lessons Learned

SECTION V: Design

Setback: Considerations

 (Average width = 3.1 m / 10.3 ft) Source: Rails-to-Trails Conservancy

FIGURE 5.5 Width of RWT, by percentage of trails

FIGURE 5.6 Setback and separation definition

 (Average = 10.1 m / 33 ft) Source: Rails-to-Trails Conservancy

FIGURE 5.7 Distance between edge of trail and track centerline, by percentage of trails

The term "setback" refers to the distance between the edge of an RWT and the centerline of the closest active railroad track while "separation" refers to the treatment of the space between an RWT and the closest active railroad tracks, including fences, vegetation, ditches, and other items (see Figure 5.6). When determining the minimum setback for a RWT, factors to consider include train speed and frequency, maintenance needs, applicable State standards, separation techniques, historical problems, track curvature, topography, and engineering judgment.

The range of trail setback on the existing RWTs varies from less than 2.1 m (7 ft) to as high as 30 m (100 ft) (see Figure 5.7), with an average of almost 10 m (33 ft) of setback from the centerline of the nearest track. A comparison of RWT setback distance to both train speed and frequency reveal little correlation; over half (33 of 61) of the existing RWTs have 7.6 m (25 ft) or less setback, even alongside high speed trains (see Figures 5.8 and 5.9). Many of the trails with little setback are ones that have been established many years. The trail managers for these well-established trails report few problems. However, interviews with train engineers in several areas indicate that they observe a tremendous amount of daily trespassing and problems in areas with little setback and no physical separation.

In comparison, RWTs in Perth, Australia, are typically 3 m (10 ft) wide, and separated from the adjacent railway line by a 1.8 m (6 ft) high chain link fence with three strands of barbed wire. The minimum setback from track centerline to the fence is 4.5 m (15 ft).

Researchers attempted to determine if narrower setback distances have a direct correlation to safety problems. However, based on the almost nonexistent record of claims, crashes, and other problems on any RWTs, they were unable to determine a correlation between setback distance and trail user safety. An FRA study on the impact of high train speed on people standing on boarding platforms concludes that induced airflow is a safety issue for a person within 2 m (6.5 ft) of a train traveling at 240 km/h (150 mi/h) (Volpe, 1999).

There is no consensus on either appropriate setback requirements or a method of determining the requirement. Some trail planners use the AASHTO Bike Guide for guidance. Given that bicycle lanes are set back 1.5 to 2.1 m (5 to 7 ft) from the centerline of the outside travel lane of even the busiest roadway, some consider this analogous. Others use their State Public Utilities Commission's minimum setback standards (also known as "clearance standards") for adjacent walkways (for railroad switchmen). These published setbacks represent the legal minimum setbacks based on the physical size of the railroad cars, and are commonly employed along all railroads and at public grade crossings. The minimum setback distance is typically 2.6 m (8.5 ft) on tangent and 2.9 m (9.5 ft) on curved track. However, FRA and railroad officials do not consider either of these methods to be appropriate for an RWT. This is because AASHTO's guidelines for motor vehicle facility design are not seen as comparable to rail design, and the setback distance for the general public should be much greater than that allowed for railroad workers.

 FIGURE 5.8 RWT setback/train speed correlation FIGURE 5.9 Setback/frequency correlation

Further considerations when determining setback requirements may be physical constraints on or adjacent to railroad corridors, presence of separation techniques such as fencing, historical trespassing, and other problems. Finally, train densities can change at any time and location, and railroads require flexibility in their operations to meet customer requirements. Structures or right-of-way modifications that impede a railroad's ability to change or control its operations are unacceptable.

FIGURE 5.10 Minimum RWT setback depends on specific situation

FIGURE 5.11 Dynamic envelope delineation (MUTCD Fig. 8A-1. Note: no dimensions given in MUTCD.)

Setback: Recommendations

Because of the lack of consensus on acceptable setback distances, the appropriate distance must be determined on a case-by-case basis (see Figure 5.10). Trail planners should incorporate into the feasibility study analysis an analysis of technical factors, including:

• Type, speed, and frequency of trains in the corridor;
• Separation technique;
• Topography;
• Sight distance;
• Maintenance requirements; and
• Historical problems.

Another determining factor may be corridor ownership. Trails proposed for privately-owned property will have to comply with the railroad's own standards. Trail planners need to be aware that the risk of injury should a train derail will be high, even for slow-moving trains. Discussions about liability assignment need to factor this into consideration.

In many cases, adequate setback widths, typically 7.6 m (25 ft) or higher, can be achieved along the majority of a corridor. However, certain constrained areas will not allow for the desired setback width. Safety should not be compromised at these pinch points ? additional barrier devices should be used, and/or additional right-of-way purchased. In the case of high speed freight or transit lines, RWTs must be located as far from the tracks as possible and are infeasible if adequate setbacks and separation cannot be achieved.

 FIGURE 5.12 Minimum RWT setback - fill sections (depending on situation) FIGURE 5.13 Minimum RWT setback - constrained sections (depending on situation)

At an absolute minimum, trail users must be kept outside the "dynamic envelope" of the track - that is, the space needed for the train to operate (see Figure 5.11). According to the MUTCD (Section 8), the dynamic envelope is "the clearance required for the train and its cargo overhang due to any combination of loading, lateral motion, or suspension failure." It includes the area swept by a turning train.

Relatively narrow setback distances of 3 m (10 ft) to 7.6 m (25 ft) may be acceptable to the railroad, RWT agency, and design team in certain situations, such as in constrained areas, along relatively low speed and frequency lines, and in areas with a history of trespassing where a trail might help alleviate a current problem. The presence of vertical separation or techniques such as fencing or walls also may allow for narrower setback.

Updated: 2/11/2014
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