Access Management

How do we improve the safety and capacity of a road system without expensive widening and purchase of property and people’s homes? One technique that’s come to the forefront today is access management. Extensive research and ever-increasing experience show that reducing traffic turmoil by better control of access significantly reduces accidents and increases capacity.

And what is access management? The Transportation Research Board’s Access Management Manual defines access management as “the systematic control of the location, spacing, design, and operation of driveways, median openings, interchanges, and street connections to a roadway. It also involves roadway design applications, such as median treatments and auxiliary lanes, and the appropriate spacing of traffic signals.”

There are many reasons why access management is vital. It extends the life of roads and streets and protects the public’s investment in its system. When development occurs along a road and driveways begin to proliferate, capacity and safety decrease drastically. The accident rate of a four-lane road like Colerain Avenue with all its driveways is 4 to 6 times the rate of a similar road where access is managed. And managing access on a four-lane road is equivalent to adding two more lanes of capacity, and at a cost far less than that required to add lanes. Even if one weren’t concerned about maintaining existing roads and streets, the likelihood of obtaining large sums of money to widen and/or replace existing roads is decreasing as transportation infrastructure needs and costs continue to outpace available funding.  

Figures 1 and 2 illustrate why access points contribute to congestion and accidents. They are called conflict diagrams; they show all of the conflicts that occur at an intersection where the paths of vehicles moving through cross, merge with or diverge from one another. At a typical 4-way intersection (Figure 1), there are 32 conflict points, 16 of which are the crossing type where one vehicle could impact the side of another. For a 4-way intersection on a 4-lane road, add 8 more crossing-type conflict points for a total of 40.

A tee intersection where a drive or side street is on only one side (Figure2) has 9 conflict points, and 11 when the main street is 4-laned. Five of the 11 are crossing-type conflicts.

When traveling on a road like Colerain Avenue with more than 60 access points per mile, each driver is challenged by approximately 1,000 conflict points per mile of travel. This condition results in considerable congestion and delay as drivers maneuver to avoid the conflict points and a considerable number of accidents when drivers fail to avoid them. It results in turbulence and friction which in turn raise driver tension, and when driver tension is increased, the potential for tip-over into road rage is increased as well.  

Figures 3 and 4 illustrate the conflict points at the 4-way and tee intersections when these access points become right-in/right-out. The reductions are dramatic and result in significantly improved traffic flow resulting in markedly reduced congestion and accidents. And, in a more general way, they illustrate why the development of standards and policies establishing access management are very important if the integrity and safety of our road system are to be maintained.

Colerain Avenue is currently undergoing a retrofit improvement project to address the congestion and safety problems that have grown over the last 40 years as development occurred without access management. While some similar development has also occurred on the county road system, there is a much greater opportunity to avoid many of the congestion and safety problems by planning ahead. The Hamilton County Engineer’s Office is doing just that.

Developing Access Management Regulations

The Hamilton County Engineer’s Office worked with an Access Management Advisory Group to create standards, policies and procedures for access management regulations. The regulations will cover the Hamilton County road system and some township roads.

The process began in October 2003, when the County Commissioners adopted a resolution proposing the consideration of access management regulations. This was followed by solicitation of potential members to serve on the Advisory Committee and a formal opening public workshop in early December.

Shortly after the public workshop, the County Commissioners appointed Advisory Committee members including registered surveyors, representatives of the homebuilding industry, licensed realtors, representatives of the Hamilton County Regional Planning Commission, professional engineers with traffic expertise, a representative of the OKI Regional Council of Government, several township trustees, a member of the Board of County Commissioners, and the Hamilton County Engineer and representatives of his office.

The committee, which had 27 members, represents the many areas and fields of endeavor with an interest in access management, and the many different viewpoints assure that proposals are evaluated and discussed. Niehaus Transportation Engineering served as consultant to the committee.

The committee met every other week.  The regulations were developed for each of six categories of roads on the existing Hamilton County Thoroughfare System. These categories include the following (with examples):

• Expressways:  Five Mile Road (portion), Reed Hartman Highway
• Major Arterials:  North Bend Road , Winton Road , Kenwood Road
• Minor Arterials:  Cheviot Road , Compton Road, Eight Mile Road
• Major Collectors:  West Fork Road , Daly Road , Drake Road
• Minor Collectors:  Reserved for selected township roads & streets
• Local Roads:  Primarily serving abutting properties

Also determined at this time are access connection definitions (roads & streets, drives, etc.); access classification definitions, ranging from minimum-volume drives up to high-volume drives and streets; minimum signal spacing; minimum road or street spacing; minimum full-access driveway spacing; right-in/right-out requirements; corner spacing; left-turn lane and right-turn lane requirements; and lateral access restrictions. All of the requirements will be shown on matrices, one for each functional classification, as supplemented by text material.