Chapter Four - Section 4
Trail Design Guidelines: Multi-Use Corridors
In reality, many of the trails implemented in the state of Iowa will be multi-use trail corridors. The classic example of a recreational trail a long linear pathway connecting parks or communities is a multi-use trail used by bicyclists, walkers, in-line skaters, and, possibly, snowmobiles in the winter. There are two types of multi-use trails:
- Single-treadway corridors have only one trail facility, which is planned to accommodate all desired modes.
- Dual-treadway corridors accommodate a variety of modes on two or more different trails.
The former example is the most cost effective, but can only be used when the user modes are reasonably compatible with each other. The latter example allows for separation of uses within a corridor. This can reduce conflict and still accommodate varied users. The dual treadway corridor may also provide the same support services, such as trailheads, restrooms, and rest areas, for many different users, thereby economizing trail development. It does, however, require a wider right-of-way.
Single-treadway corridors are the simplest type of trail, providing a single recreational facility within a corridor that may not be much wider than the trail itself. On these types of facilities, it is important to control the uses that take place, as incompatible user modes will cause serious conflict on a relatively narrow facility.Compatible Modes
The following are examples of user modes which may occur on the same single-treadway corridor. There may be other possibilities, depending on the design of the trail and community desires.
- Pedestrians, bicyclists, and in-line skaters on a paved multi-use trail facility. This is the classic example of a multi-use trail, and conflicts are relatively rare. Depending on the volume of traffic, however, pedestrians may need to be separated from faster moving bicyclists and skaters for their own safety (see "Pedestrian Trails").
- Pedestrians and bicyclists on a granular trail with snowmobiles in the winter. The seasonal offset of these uses makes them compatible.
- Pedestrians, bicyclists, and in-line skaters on a paved trail with snowmobiles in winter. The sharing of a trail in this way is possible, but snowmobiles with studs may cause severe damage. In some areas, paved trails are plowed to provide a recreation or transportation amenity even in winter. In this case, snowmobiles must be disallowed.
- Equestrians and snowmobiles. The seasonal offset of these uses makes them compatible.
The guidelines for single-treadway corridors are simple: of the user modes planned, the most stringent guidelines should be used. If pedestrians are one of the designated users of the corridor, accessible facilities should be developed that meet the needs of older adults and people with disabilities. This should hold true even if pedestrians are not the primary trail users. This applies even to multi-use trails where users have a seasonal offset.
Dual-treadway corridors are used when incompatible uses coexist in the same corridor. In these cases, it is important to provide more than one trail, each tailored to the unique needs of a use mode or group of use modes.Incompatible Modes
Incompatible uses may be a result of drastically differing speeds, trail surface needs, or volume of users. The following list of incompatible modes shows those uses which warrant separate treadways if both are planned in one corridor.
- Bicyclists/pedestrians and equestrians. These two user types have different requirements for trail surface, and bicycles and pedestrians may frighten horses.
- Bicyclists/pedestrians and OHV/motorbike users. These two user types have greatly different average speeds, which could create hazards for both groups. In addition, the two groups require different trail surfaces.
- Equestrians and OHV/motorbike users. Despite the similarity of trail design for these two modes, the speed and noise of OHVs and motorbikes could frighten horses.
- Pedestrians and bicyclists/in-line skaters. If traffic volume on a trail is very high, dangerous conflicts can occur. In cases of high traffic volume, the multi-use trail should be split into separate trail facilities for these two groups (see "Bicycle Trails" and "Pedestrian Trails").
When dealing with dual treadways, there are two issues to consider.
- The design of each treadway.
- The separation of the various treadways.
The design of each treadway is similar to that described above under "Single-Treadway Corridors." Each treadway should follow the most stringent guidelines, based on the user modes it will host. In addition, each treadway should be wide enough to permit users to travel in both directions.
The separation of treadways varies with local conditions and planned user modes. The following is a brief list of some common dual-treadway corridors and recommended separations.
- Separation between multi-use trails and equestrian trails: 2 feet or greater, possibly with a fence or planted median between them (clear zones from each trail to any fence or tree should be maintained) (see Figure 4-22).
- Separation between multi-use trails and OHV/motorbike trails: distance is variable, but a vegetative buffer or fencing should be provided (see Figure 4-23).
- Separation between paved trails and adjacent snowmobile trails: none required, but edge of paved surface should be clearly marked in winter (see Figure 4-24).
- Equestrian and OHV/motorbike trails: as far apart as possible, with vegetative buffer or fencing provided (see Figure 4-25).
- Pedestrian trails and bicycle/in-line skating trails: at minimum, a solid white stripe; 2-foot break in pavement preferred (see Figure 4-26).