The Minnesota Department of Transportation defines access management as “the planning, design and implementation of land use and transportation strategies in an effort to maintain a safe flow of traffic while accommodating the access needs of adjacent developments.” In plain English, access management is the practice of limiting driveway or street intersections on a road to avoid crashes and congestion.
A helpful aid in determining what sort of access management a road requires is to place it on a chart showing the ratio between its access, the ability to get onto the road, and mobility, the speed and efficiency of the road. Freeways sit on one end of the access management spectrum. Interchanges are spaced out in a way that greatly limits access, which promotes faster, better flowing traffic. Local residential streets are at the other end of the spectrum, where closely packed ingresses, such as driveways, are expected. Between these two extremes are the various other road types, each with its own unique balance of access and mobility. It is on these roads that good access management policy can help improve the flow of traffic while still providing reasonable access to private property.
Whereas good access management can create a great functioning road, poor access management can lead to traffic congestion. In these cases multiple vehicle conflicts from uncoordinated turning movements create congestion and safety issues. Property owners realize that these problems can have a huge impact on a person’s choice to travel to a given area. This can reduce the number of clients a business gets, frustrates local residents, impact the livability of the neighborhood, and slow deliveries. In contrast, effective access management provides the following benefits:
- Reduced congestion and better overall traffic flow
- A lower potential for crashes as there are fewer places where cars cross paths with other cars, as well as with pedestrians
- Added capacity, which could reduce the number through lanes needed and, in turn, reduce the chance of crashes
- Decreased travel times for commuters, truck drivers, and others
- Easier movement between properties, improving the livability of adjacent neighborhoods
The effect of access management on non-motorized traffic can be mixed. Any reduction in the number of driveways, or full access intersections, reduces the number of vehicle conflicts. However, that same access reduction can also lead to higher vehicle speeds, impacting the comfort, and increasing safety concerns for pedestrians and bicyclists. This is why good access management and design should consider non-motorized traffic as well as mass transit use in the area.
Different features that support and create a safe environment for pedestrian, bicycle, and transit use, can be incorporated into any access management plan. Such design elements could include a small driveway radius, having driveways ramp up to the sidewalk rather than the opposite, and orientating driveways at 90 degrees to sidewalks or crossings.
Good access management will look into the possible future of a site under development. Taking a long term view of accessibility to the property will help ensure future prosperity of the area. Driveways close to a signalized intersection, for example, may seem fine now, but in time may become blocked by growing vehicle queues as traffic loads increase. A traffic impact study is often the best method of determining the need for access management as well as what shape that management should take.
To assist in the planning of new developments, it is recommended that every agency develop their own access management policy so that developers, architects, and engineers know in advance the guidelines that should be used when creating new driveways and street connections.
Access management techniques, such as installing raised medians or pedestrian crossings, should be included in any study that deals with major reconstruction or roadway expansion projects. A traffic study should also be done on sites with existing safety concerns or congestion to determine the cause and extent of the issue. After the study is complete look at the data to determine what access management techniques, if any, will solve the problems that have been discovered. Being mindful that you are designing for more than just the cars that will use the road will lead to superb design.
Components of Access Management
- Facility hierarchy: Determine where on the hierarchy of thoroughfares (principal arterial, arterial, collector, or local road) a road is, to help define its balance between mobility and access. All agencies should have defined these categories in their policies or comprehensive plan.
- Intersection spacing: Establish the location of public intersections as well as which intersections will be controlled with traffic signals, all-way stops, or roundabouts.
- Driveway spacing: Decide the location of driveways and how close to the public intersections they should be, as well as proximity to other driveways.
- Public and private intersection types: Determine which vehicle movements will be allowed at each intersection. Preventing some movements through ¾-access (allowing left and right turns from the main road but only right turns from the driveway or side street) or right-in/right-out only access (allowing only right turns from the main road and from the driveway or side street) maybe desirable at some locations.
- Overall development of connectivity: In order for access management to work, smaller properties must have some type of access to the remaining median openings and signals.
Access Management Techniques
- Creating connectivity between adjacent commercial properties to better serve businesses with reduced road access, such as a frontage or backage road connecting several properties.
- Consolidating private driveways, either through shared access or reduced access.
- Providing a center median to limit access, including retrofitting a two-way left turn lane.
- Using exclusive turn lanes to remove turning vehicles from the through lanes.
- Creating service roads to better access various properties.
- Limiting street and driveway connections to right-in/right-out, or ¾ accesses.
- Using roundabouts to allow for easier U-turns compared to traditional intersections.
Resources
- Institute of Transportation Engineers Access Management
http://www.ite.org/technical/IntersectionSafety/access.pdf
- Federal Highway Administration Access Management
http://www.ops.fhwa.dot.gov/access_mgmt/
- Federal Highway Administration Proven Safety Countermeasures
http://safety.fhwa.dot.gov/provencountermeasures/fhwa_sa_12_006.htm
- Transportation Research Board Committee on Access Management
http://www.accessmanagement.info/
- Minnesota Department of Transportation (MnDOT) Access Management
“In plain English, access management is the practice of limiting driveway or street intersections on a road to REDUCE avoid crashes and LESSEN congestion.”
Another critical issue you could mention is reduction of conflicts that can result in severe injuries such a left turns and crossing movements.
Roundabouts, beside the U-turn support, convert left turns and crossing maneuvers to right turns. Right turn related crashes rarely result in injuries.
“Overall development of connectivity: In order for access management to work, smaller properties must have some type of access to the remaining median openings and signals.” This is not a principle of access management. What AM recommends is a combination of on-site circulation, cross easements between properties, and a good secondary street system to provide for property access that then leads to arterial access. Since the 1950’s AASHTO has not recommended private driveway connections to arterials. They have occurred anyway because 1. retailers want direct access to high traffic flows on arterials and 2) many municipalities and rural areas did not have the capital to establish secondary streets, so only the state highway existed and was paved.
There is no such thing as a safe access connection to an arterial. Every one is a safety hazard to some degree – and therefore careful management of the location, design and allowed operation is critical to public safety.
Hi Mr. Demosthenes, Our local planning board does not have any experience with access management or safe planning – and you have articulately stated the case for careful planning – can I please quote you to them in my remarks? Can I use your title (which I do not know) since you obviously have the sophistication and experience to speak with authority and knowledge. Many thanks, Mitch Fox (mbfox99@gmail.com)