Access Control

In keeping with theme of increased safety for both drivers and pedestrians from my pervious post on roundabouts, this weeks post will be on access control. When we talk about access control what we are really talking are the following elements:

  • Driveways
  • Medians
  • Median Openings
  • Traffic Signals

These elements define what the access control is along a road corridor. In Tennessee there are many examples of heavily traveled routes that have  five lanes. These five lanes include two lanes of traffic going one direction, two lanes of traffic going the opposite direction, and a continuous left turn lane in the center for either direction, often refered to as a “suicide lane”. Examples of this kind of road include Nolensville Road in Nashville, Kingston Pike in Knoxville, and Park Avenue in Memphis.

I live near Nolensville Road in Nashville and can tell you that during peak traffic that it is not a fun road to drive on to get to businesses there, and it is even more dangerous to pedestrians trying to cross the street. Access control elements that probably cause the most congestion and affect safety include: a center two-way left turn lane, left turns that can be made from any driveway, and the high number of driveways along this road. There are alternatives to this “driveway madness” and they involve access control.

As you can see in the diagram, limiting access by using medians can dramatically reduce the number of “conflict points” or places where there is a potential for an accident. There is a strong case for limiting the number of driveway openings, and for adding medians:

  • Crash statistics have shown that more access/driveways (per mile of road) can result in more crashes (per mile of road).
  • More access/driveways can result in slower speeds, due to the drivers being more aware that a car may pull in front of them from the many driveways.
  • Medians make crossing the road for pedestrians much safer; instead of crossing four or five lanes of traffic at once, pedestrians can cross two lanes of traffic and wait in the median if they need to in order to finish crossing the road.
  • By including limited landscaping you can make a road section much more aesthetically pleasing, which better helps develop a sense of community.
  • Access control allows a community to better manage growth and development.

Businesses with frontage along a major road (such as Nolensville Road) typically oppose any restriction in access control in front of their property. If it involves losing a driveway or having a median installed in the road (thereby preventing any left turns), property owners believe that their business with suffer. Personally I feel the opposite way. I avoid areas and businesses where I don’t feel safe driving, such as road with high traffic volumes, with a high number of driveways and no median that restricts the left turns.

I much prefer driving to businesses along roads that have better control of driveways, and raised medians that only allow me to turn left at specific locations. I believe an example of a road with good access management is Mallory Lane in the Cool Springs Mall area in Brentwood. Now trust me, I have experienced traffic on this road (think before Christmas!), but Mallory Lane does a good job of limiting where left turns can happen, and succeeds in limiting the number of driveways. From what I understand Park Avenue in Memphis has sections that are good about access control, and sections that are not so controled.

I understand that some reading this post may disagree on the concept of access control, and I can understand that. The only thing that I can sincerely claim that I am an expert on is my opinion.


About arran375

I work for Askew, Hargraves, Harcourt and Associates, Inc. here in Nashville, Tennessee. The short version of what I do is that we help local governments spend the Federal funds they get from TDOT on road, and bridge projects.
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