Every driveway and street connection is a potential conflict point among motorists, bicyclists and pedestrians. Therefore, managing the number, spacing, access, directional flow, and other aspects of driveway and side street connections protects those traveling along the corridor from conflicts with those entering or leaving the corridor. Access management strategies such as providing raised/non-traversable medians and limiting driveway access may be useful in promoting safe bicycle travel, particularly on arterial or major collector streets, since they help reduce the number of potential conflict points.
The principles of access management incorporate providing specialized roadways appropriate to their intended use. The trade-off is between providing direct access and promoting through movement. For example, the main purpose of freeways and arterials is to move through traffic, and access should be restricted to necessary interchanges. Local streets should generally serve all destinations and access should not be limited. There are exceptions, however, if management is needed to reduce non-local traffic or create preferential bicycle boulevards (see Traffic Diversion). Access management includes such measures as limiting the number of or establishing minimum spacing between driveways; providing for right-in, right-out only movements; locating signals to favor through movements; restricting turns to certain intersections; and using non-traversable medians to manage left- and U-turn movements. Other measures such as provision of left and right turn lanes at intersections to remove slowing/turning vehicles from the traffic stream could also be included. Hodgson, et al., have provided an in depth discussion of potential impacts (positive and negative) of access management strategies on bicyclists and pedestrians.12 The Transportation Research Board (TRB) Committee on Access Management identifies 10 principles or strategies of access management altogether, along with the rationale and elements of a comprehensive program (see http://www.accessmanagement.gov/). TRB also published the Access Management Manual in 2003 that provides a comprehensive description of access management principles, techniques and effects, and rationale and steps toward developing an access management program and policies.13 Safety and other impacts of access management are documented in National Cooperative Highway Research Report 420.14
- Reduce conflicts between those traveling along the corridor and those entering or leaving the corridor.
- Provide access appropriate to the function of the roadway and area it serves.
- Maintain flow of traffic along a corridor.
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- Consider whether the street's intended function is primarily to move through vehicles (freeways, arterials, collectors) or to provide direct access (neighborhood and local streets).
- Providing for free-flow of traffic by reducing connections may result in increased travel speeds.
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If included in initial design and construction, access management measures might raise or decrease costs compared to other designs. Cost of retrofit measures would depend on the type and extent. Adding a raised median, for example, is estimated to cost $15,000 to $30,000 per 30 m ($15,000 to $30,000 per 100 ft). Prohibiting left turns with diverters may cost from $15,000 to $45,000 each.
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