Plan, Design, Build
Crossings and Intersections
Crossing design is one of the most important components of trail planning. Safety, in particular, is always a priority when designing a crossing, since there is potential conflict between wide varieties of users.
A good first resource for crossings is the Guide for the Development of Bicycle Facilities, produced by the American Association of State Highway and Transportation Officials (AASHTO), which provides guidelines for traffic engineers designing bicycle facilities (see "Additional Resources" box to the right for more information). It includes a section on intersections and crossings. The AASHTO guide addresses three types of crossings: midblock, adjacent path and complex. These crossings can include public roadways, private driveways and railroads.
- Midblock crossings
This type of crossing is the simplest and most common, and it involves a trail crossing a roadway or railroad when there are no other adjacent intersections or crossings. There are two types of midblock crossings: perpendicular crossings, which occur when the trail and the roadway intersect at right angles, and skewed crossings, which occur most often when the trail and the roadway intersect at an angle. Skewed crossings usually require a swerve in the trail path so that the trail crossing itself is perpendicular to the roadway.
- Adjacent path crossings
These crossings occur most often when a trail, running parallel to a roadway, crosses an existing roadway intersection. Due to the presence of turning vehicles, this type of crossing presents more challenges than a midblock crossing. Appropriate signage, traffic signals and distance between the roadway intersection and the trail crossing often play important roles in the design of adjacent path crossings.
- Complex crossings
This category acts as a catch-all for most crossings that cannot be categorized as midblock or adjacent path crossings. Due to the nonstandard challenges these crossings often present, the AASHTO guide instructs engineers to treat these crossings on a case-by-case basis.
One of the advantages of using a trail is that it provides a dedicated right-of-way that minimizes interactions with vehicles and signalized intersections. An important consideration to remember when designing a trail crossing is that many trail users, especially cyclists desiring to maintain momentum, may have a low tolerance for long delays at crossings. In addition, children using the trail may not be aware of traffic rules. Crossings should also be ADA-accessible so they can be used by all trail users. When planning a crossing, be sure to design with these considerations in mind.
The thermoplastic striping used to demarcate a crossing on a roadway is one of the most important design considerations at intersections. While standard crosswalk markings such as zebra, parallel line or hybrid "ladder" crossings are effective at alerting drivers to crossing traffic, standard crosswalks along a multi-use trail often leave a gray area. Drivers, seeing a standard pedestrian crosswalk, may expect cyclists to dismount before crossing. Yet cyclists, who are riding on a multi-use trail, may see dismounting at every crossing as unreasonable. In addition, laws regarding cyclists in crosswalks are often muddy and vary from state to state.
Instead of striping a standard crosswalk, some trails use nonstandard crosswalk patterns in locations where cyclists are expected to ride across a roadway instead of dismounting and walking across. One example is the Washington & Old Dominion Trail in northern Virginia, where crossings are marked with parallel dashed lines instead of parallel solid lines. Nonstandard striping indicates to drivers and trail users that the crossing is different than a standard crosswalk situation. Crossings are typically striped by the road's managing agency, usually a local or state department of transportation or public works. Any provision for nonstandard striping or any striping at all must be made with the managing agency.
Crossings as Rest Areas
Depending on the crossing and the nature of the roadway being intersected, crossings can act as rest points. For example, there may be a bus stop at the crossing, or the crossing may act as a pick-up and drop-off spot. As William H. Whyte observed in his landmark book City, people like to congregate at corners and junctions, even if those locations are noisy or already congested. When designing crossings, be aware of this behavior and, if possible and desired, create designated "rest areas" at crossings so that those waiting or socializing at a crossing do not interfere with others who are looking to continue along the trail. Having rest areas at crossings where people can stand or sit will also alert drivers of pedestrian and cyclist activity in the area, encouraging them to slow down and create a safer environment for all.
Alerting Drivers and Trail Users to a Crossing
An important issue when designing a crossing is ensuring that drivers, who usually control the fastest and heaviest vehicles involved in the crossing, are aware of the presence of trail users. Trail users, especially cyclists and joggers, also have a responsibility to slow or stop before a crossing to ensure the safety of themselves and others. These overlapping goals can be accomplished in a number of ways. The first and most obvious tool is signage, both on the intersecting road and along the trail itself, to warn road and trail users of an upcoming crossing.
Signage is not the only, or often the best, way to create safer crossings. The Manual on Uniform Traffic Control Devices (MUTCD) states that "the use of warning signs should be kept to a minimum as the unnecessary use of warning signs tends to breed disrespect for all signs." In addition to signs, pavement treatments and other, more permanent traffic-calming measures on both the road and the trail are alternative methods to improve driver and trail user recognition of crossings.
On a trail, these steps can take the form of "rumble strips" that alert cyclists to slow down, or more significantly, a swerve in the trail to force cyclists to slow down. On the road, different pavement treatments, including coloring or special materials, can alert drivers. If a more drastic change is necessary, speed tables or speed humps can be used as traffic-calming measures near trail crossings. When considering textured pavements or traffic calming, be sensitive to the needs of trail users. Inline skaters, for example, often have problems with rumble strips and textured pavement.
Another option to reduce speed at crossings is the use of medians, both on the trail and on the intersecting roadway. Low medians on a trail can narrow the pathway as it approaches a crossing, forcing trail users to slow down while still allowing access for emergency vehicles. Medians on the intersecting roadway can reduce the speed of crossing automobiles and provide a refuge for trail users as they cross a street.
For some trail managers, a major issue is restricting the number of private crossings. In areas where there is rapid development, adjacent landowners may seek to cross a trail to allow vehicular access to their property. A high number of crossings can have an adverse impact on trail users. It is important that trail managers anticipate this issue and determine where trail crossings are appropriate and what mechanisms can be used to limit an excessive number. Meeting with local departments of transportation, public works and planning are essential to this effort. Sometimes, agreements with these departments can become official department policy and even get adopted by the city or town council.
Some states also have laws protecting crossings or takings of parks and recreation areas if there is a feasible and prudent alternative to the proposed crossing. When trails have been designated as government-owned parkland, these laws have been used to minimize the number of trail crossings. In addition, rail-trails on railbanked corridors can be reactivated for rail use in the future. For this reason, crossings of these corridors can be treated as potential railroad crossings and can be limited to only the most necessary cases.
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