What are the issues where a trail crosses a road?

The safety goal at any crossroad is that users on crossing approaches become aware of the intersection sufficiently in advance to prepare as necessary and make their crossings in an ordered and predictable sequence that avoids conflict and crashes. This concept is sometimes called sight distance.

To calculate the minimum sight distance bicyclists on a shared use path (such as a bicycle trail) might need to stop for a potentially conflicting event, designers customarily consult an equation presented in the AASHTO Guide for the Development of Bicycle Facilities. The equation is described in a number of state highway and bicycle facility design publications.

Priority is commonly assigned to vehicular users (motorists and bicyclists) by means of Stop or Yield signs installed on the approaches where users are required to yield. On the approaches not required to yield, warning devices are usually installed (and may also be installed on the other approaches). As a general rule, the least restrictive control that adequately regulates crossings should be used. Users are more likely to comply with controls and avoid conflicts when they can see the other approaches. Perpendicular intersections promote visibility and reduce trail crossing distance. Centerline markings on the trail approaches can help order trail traffic flows and avoid conflicts with oncoming users.

For pedestrian users of a trail, state traffic code crosswalk rules are usually considered to apply at a crossing, and crossings are commonly marked as crosswalks.

High traffic volumes at the crossing may warrant a signal. In that case, delays and conflicts can be eliminated (at considerably higher cost) by providing a grade-separated crossing.

The Manual on Uniform Traffic Control Devices provides standards and guidance for the use of Stop, Yield, and intersection warning signs on shared use paths in Chapter 9B. Use of regulatory and warning signs on roadway approaches is covered by the MUTCD's general standards and guidance for use of such signs (chapters 2B and 2C).