摘要: |
Transportation access management is defined as systematic control of the design, spacing,
operation, and locations of street connections, interchanges, driveways, and median openings on
the roadway with the purpose of providing vehicle access while preserving the efficiency and
safety of the entire transportation system. Access management is a proven method for
maintaining and improving roadway capacity; traffic flow; and the safety of traffic, pedestrians,
and bicyclists on rural and urban highways and streets (1). Improvements to operational
efficiency and safety reduces transportation costs. Reductions in delay and improvements to
traffic flow also reduces vehicle emissions, reducing the environmental impacts of
transportation. Research has shown that access management related improvements to traffic
operations and safety have a positive impact on the local economy (2).
Access management methods include, but are not limited to, increasing the spacing between
signals and intersections, managing access to/egress from driveways, median treatments
2
(including the use of medians, indirect left-turns, etc.), use of frontage roads, providing turn
lanes for heavy traffic movements, and land use policies. Each of these methods has safety and
operational impacts (leading to financial and other benefits) as well as associated financial costs
for implementing the changes and compensation to landowners for lost property or access. The
decision of whether to implement a change often depends on the overall cost as well as the
comparison of the cost relative to the expected benefits of the change. These benefits include the
current and future benefits to both the public and the agency making the changes. Also, the
project must fit within the overall budget of the agency making the changes.
Currently, no locally calibrated tool for South Dakota exists that captures the complexity of the
current and future public benefits of proposed access management for estimating the financial
and other benefits and comparing them with the associated financial costs. The benefits may be
related to many local conditions including land use and zoning, roadway type and functional
classification, traffic volumes, pedestrian and bicyclist volumes and characteristics, and the
locations and other characteristics of access points. Given that many outcomes (i.e., safety and
traffic operations) are related to human factors that are often unaccounted for in research,
estimates of safety effects and operational changes associated with general access management
methods provided in the Highway Safety Manual (3) and the Access Management Manual (4)
may not be applicable in South Dakota. Also, more specific, complete estimates of the effects of
access management methods on public benefits that are locally calibrated are desired when
making decisions related to the value of the investment. |