The result is a series of recommended desirable minimum curve radii for corners that should be safe for bicyclists. Another critical factor in trail design is the grade or slope of the path. The ability of a cyclist to stop or slow down to avoid a collision or crash is affected by many things. The rider must have time to identify a potential problem and react accordingly, which means that they must be able to see approaching intersections or corners in plenty of time even when they are traveling at the design speed of the trail. In response to a message about trail maintenance posted recently to an e-mail listserve, one trail manager identified the three most important issues as draining, drainage and drainage.
Poor drainage can ruin a good trail.
A hard surface, such as cement or asphalt, will generally see cyclists operating at a faster speed than a soft surface, but may not be as popular with joggers and is more expensive to install. Factors such as weather conditions and soil types can affect the choice of asphalt, concrete, or crushed rock. However, not all corridors have this asset and structures of all kinds are needed to carry trail users under or over obstacles such as highways, rivers, freeways etc. Obstacles such as major highways or rivers are hard to overcome and present the designer with many challenges. However, unless obstacles such as these are overcome, trails have limited value and use.