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21st Century Operations Using 21st Century Technologies

What is Access Management?

Access Management

Access Management (AM) is the proactive management of vehicular access points to land parcels adjacent to all manner of roadways. Good access management promotes safe and efficient use of the transportation network. AM encompasses a set of techniques that state and local governments can use to control access to highways, major arterials, and other roadways. These techniques include:

  • Access Spacing: increasing the distance between traffic signals improves the flow of traffic on major arterials, reduces congestion, and improves air quality for heavily traveled corridors.
  • Driveway Spacing: Fewer driveways spaced further apart allows for more orderly merging of traffic and presents fewer challenges to drivers.
  • Safe Turning Lanes: dedicated left- and right-turn, indirect left-turns and U-turns, and roundabouts keep through-traffic flowing. Roundabouts represent an opportunity to reduce an intersection with many conflict points or a severe crash history (T-bone crashes) to one that operates with fewer conflict points and less severe crashes (sideswipes) if they occur.
  • Median Treatments: two-way left-turn lanes (TWLTL) and nontraversible, raised medians are examples of some of the most effective means to regulate access and reduce crashes.
  • Right-of-Way Management: as it pertains to R/W reservation for future widenings, good sight distance, access location, and other access-related issues.

Access Management provides an important means of maintaining mobility. It calls for effective ingress and egress to a facility, efficient spacing and design to preserve the functional integrity, and overall operational viability of street and road systems.

Figure 1: This figure is a conceptual roadway functional hierarchy showing that as access increases, mobility decreases. Freeways have limited access and high mobility, whereas local streets have increased access but lowered mobility.

Figure 1: Conceptual Roadway Functional Hierarchy

 

Access Management should address the following areas:

  • Facility Hierarchy
  • Intersection and Interchange Spacing
  • Driveway spacing
  • Traffic signal spacing
  • Median treatments and median openings
  • Turning lanes and auxiliary lanes
  • Street connections

In areas of dynamic land development, it is important for jurisdictions to develop access standards that achieve a balance between property access and functional integrity of the road system. Studies show that implementing access management provides three major benefits to transportation systems:

  • Increased roadway capacity
  • Reduced crashes
  • Shortened travel time for motorists

All of the three benefits cited above are essentially the result of minimizing or managing the number of conflict points that exist along a corridor. Imagine the two extremes of the same corridor. In the least intrusive example, no minor-street conflicts exist. Traffic flows freely down an unencumbered corridor "pipe" influenced only by density, weather, and integrity of the roadway. When minor-street conflicts (i.e., "laterals") in the form of driveways and streets are introduced, the mainline flow must adjust speeds and sometimes lanes to avoid all manner of delay and conflicts introduced by the myriad combination of slowing, turning, merging, entering, and stopped vehicles. In many locations, it is necessary to completely stop the mainline flow (via signals) so the minor-street vehicles can even gain opportunity to enter the flow. In short, steady progression is interrupted, and often at uneven intervals.