Standards for Dead-End Streets

By Carol J. Thomas, AICP

How long should a dead-end street be? Why do so many subdivision regulations have a maximum allowable length of 500 feet for dead-end streets? Should the dead-end Street be discouraged? Planners and developers frequently ask these questions when unusually shaped parcels are proposed in residential developments. To provide answers to these questions, this Memo examines accepted planning and engineering practice over a 40-year period; advantages and disadvantages of dead-end streets; and guidelines appropriate to current development patterns.

Dead-end streets and cul-de-sacs generally are regulated by the rules and regulations governing the subdivision of land that are adopted by the local planning board. Cul-de-sac regulations and standards, including those listed below, must be consistent with the purposes of subdivision controls stated in enabling legislation. These purposes generally include promoting general safety, convenience, and health and welfare; ensuring sanitary conditions; providing roadways that are safe and convenient for travel; securing safety in case of fire, flood, panic, and other emergency; and securing adequate provision of municipal services.

The dead-end street is a passage that is open only at one end. The open end is usually at a through street; there usually is a turnaround at the other end; and there usually are no other ways or streets intersecting at or extending from the turnaround. The existence of the turnaround at one end gives rise to the commonly used name, "cul-de-sac." The purpose of the dead-end street or cul-de-sac is to provide access to a limited number of lots or buildings.

The cul-de-sac has advantages for developers and residents. The principal advantages are:

• Traffic volume is reduced because there is no through traffic.
• Traffic will likely travel more slowly because through traffic is eliminated.
• There is less traffic noise because the amount of traffic is reduced.
• Privacy, safety, and the value of lots along the street are increased because traffic volume, speed, and noise are reduced.
• One or more lots may be placed in the corner of a subdivision on parcels that otherwise might not have adequate frontage, resulting in more efficient use of space and fewer irregular parcels.
• Frontage is available on the end of the street as well as along its length.

There are disadvantages to the cul-de-sac, however, that frequently outweigh these advantages.

• Access to interior lots can be blocked at the open end of a dead-end street or along the cul-de-sac "spine" by an accident, stalled car or truck, fallen tree, snow pile, or construction.
• Traffic at the open end can be excessive if the street is long and access is provided to a large number of lots or buildings.
• Long cul-de-sacs (more than 500 feet) reduce the advantages since they may encourage increased traffic speeds and mid-block turning to reverse direction, turning that is frequently done in private driveways.
• Traffic has to double back, which is especially inefficient for delivery people, emergency equipment, snow plows, and service vehicles.
• Dead-end water mains encourage sedimentation and can be clogged or broken, resulting in reduced water pressure or no water service, which adds to fire hazards.
• Fire equipment, trucks, and public works equipment have difficulty maneuvering.
• Insufficient water pressure for fire fighting often results when hydrants are located only on the outside through Street or, if on the cul-de-sac, are inaccessible when the entrance is blocked. Furthermore, these conditions necessitate the use of long fire hoses, which may lower pressure and discharge rates.
• The first equipment arriving at a fire may block equipment arriving later or interfere with the maneuvering of equipment.
• The circulation plan is frequently confusing.

Because of these disadvantages, planners and engineers have agreed that cul-de-sacs should be used with caution; a second dead-end street should not branch off from a cul-de-sac (in effect, extending the dead-end street) the length of a dead-end Street should be limited (especially on slopes); a paved turnaround should be provided; consideration should be given to looping the water supply system (rather than having truncated water supply lines running from the main water line to the end of the dead-end Street); and emergency access should be provided by easements or similar means if the length of the cul-de-sac exceeds the recommended maximum.

The current standards regulating cul-de-sacs have evolved over many years. In 1939, the American Society of Civil Engineers Committee of the City Planning Division on I_and Subdivision, chaired by Harland Bartholomew, recommended that dead-end streets not exceed 300 feet in length; that they be at least 40-feet wide; and that they terminate in a circular right-of-way with a minimum diameter of 70 feet unless "the Planning Commission approves an equally safe and convenient form of paved space instead of the required turning circle."

Almost 10 years later, the American Health Association, in Planning the Neighborhood, recommended increasing the minimum length to 600 feet if the Street was wide enough for two lanes of traffic, but otherwise limiting the length of the Street to a maximum of 350 feet. In 1961, George Nez, in "Standards for New Development," recommended a maximum length of 500 feet, the current commonly accepted maximum length.

Minor variations exist. The Planners Handbook, published by the Massachusetts Federation of Planning Boards in 1972, recommends the 500-foot maximum unless, in the opinion of the local planning board or agency, a greater length is necessitated by topography. And, in 1975, the American Society of Planning Officials (ASPO) recommended that the length of a dead-end street be limited to six times the minimum lot width to a maximum of 500 feet. The ASPO recommendations went further to suggest that the street should not serve more than 14 lots.

Several authorities steadfastly maintain a standard that is the same or closer to the original 300-foot limit established in 1939. (Gallion and Eisner in The Urban Planner (1975) suggest that the maximum length of a dead-end street be 450 feet or less. The National Association of Home Builders recommends a 400-foot maximum, allowing for a range of 400 to 600 feet according to conditions, in Cost-Effective Site Planning, Single-Family Development. They also suggest that if topography dictates that the Street be longer than 400 feet, intermediate turnarounds may be advantageous. And, finally, staff members with the National Fire Protection Association, the International Fire Chiefs Association, and the U.S. Fire Administration, when interviewed, said that 300 feet was a good maximum length that should be exceeded only when a divided roadway was provided.

There are several sources, however, that recommend a more flexible standard. The Community Builders Handbook has different standards for dead-end streets with multifamily housing (a maximum of 400 to 500 feet) and for those with single-family housing (1,000 to 1,200 feet). Kenneth Halper of the American Association of State Highway and Transportation Officials (ASHTO) says that ASHTO standards give a maximum of 1,000 feet. And the Subdivision Design Standards of the Institute of Traffic Engineers gives the same 1,000-foot maximum standard.

The continuing concern with an appropriate length for dead-end streets results from a number of safety, financial, and aesthetic considerations. The roadway length must be limited to ensure the inherent advantages of cul-de-sacs (e.g., limited traffic, safety, and privacy) and to provide adequate fire protection. When a cul-de-sac is blocked, it is necessary to carry a fire hose from the collector street or the accessible hydrant closest to the blockage. If there is blockage, it is not possible to boost from pumper to pumper. Fire hoses generally lose pressure after 700 feet and can be used effectively beyond that distance only with assistance from pumpers. Seven-hundred feet of hose normally will reach the end of a 500-foot street and provide the additional length necessary to reach the rear of a building at the street end. A blockage may require men to carry ladders and equipment. This problem is severe where there are minimum manning levels, and personnel are likely to be limited in low-density areas - areas where cul-de-sacs are often prevalent. Law enforcement and ambulance access may also be blocked, greatly reducing public safety.

Service costs are higher per unit along a dead-end street because maintenance and delivery vehicles must double back. In addition to the time loss, there is a resulting increase in the cost of fuel and a minimal increase in air pollution.

The longer a dead-end street, the greater the number of persons inconvenienced if it is blocked or a water main is broken. Likewise, the greater length causes increased traffic passing a site reducing intended benefits.

Because the overriding consideration is safety, 500 feet is a reasonable maximum length for dead-end streets in urban areas. If topographic conditions are unusual, such as in hilly terrain or along canals in water-oriented communities, longer lengths may be considered. In these circumstances, extensions should be allowed only when:

• They are approved in writing by the fire chief, the superintendent of streets, and the water superintendent or similar public authority;
• The street is divided by a median;
• There is an easement from the turnaround to another street to provide a looped water system or where the system is otherwise looped; and
• There are hydrants along the cul-de-sac and at the turnaround.

Each of the above conditions should be met and in no case should the Street’s length exceed 1,000 feet.

Other standards have developed for dead-end streets that relate to the diameter of the cul-de-sac; grade; pavement width; right-of-way; median strips; and number of residential units to be served. References citing these standards are given in parentheses after the recommendation.

Diameter of cul-de-sac - Eighty-foot diameter, 50 feet of which is free of parked cars (Planning the Neighborhood); 90-foot diameter (Planning Design Criteria, Site Planning Standards, Control of Land Subdivision, Cost-Effective Site Planning; the National Fire Protection Association - Code 1, Section 1.1.1.10 - requires access for fire apparatus when the Street is more than 300-feet long); 100-foot diameter (The Community Builders Handbook and "The Cul-de-sac Pros and Cons" in the ASPO Newsletter, American Society of Planning Officials, Chicago, Ill., September 1955).

Common practice is to require a 90-foot diameter, paved. The rationale for these standards is that older fire equipment and garbage trucks may have a turning radius of only 50 to 55 feet. New fire equipment generally has a smaller turning radius. Nevertheless, in a northern climate, where snow may be plowed to the side of the paved area, the larger diameter should still be required.

Grade - Maximum of five percent (Planning Design Criteria, Site Planning Standards, Control of Land Subdivision, "Standards for New Urban Development").

Pavement Width - Twenty feet for cul-de-sacs up to 300-feet long (Residential Streets); 30 to 36 feet with a 75-foot turnaround (Planning Design Criteria, Site Planning Standards, Control of Land Subdivision "Standards for New Urban Development," Cost-Effective Site Planning).

Right-of-Way - Fifty feet (Planning Design Criteria, Site Planning Standards, Control of Land Subdivision, Cost-Effective Site Planning); 40 to 50 feet ("Standards for New Urban Development," The Community Builders Handbook).

Number of Residential Units to Be Served - Five or seven dwellings (Performance Streets, ITE Recommended Practices); 10 to 20 units (Cost-Effective Site Planning); for nonresidential areas or uses, number of vehicle trips should not exceed 100 per day (Geometric Design Guide for Local Roads and Streets).

In summary, the principal guidelines are that a dead-end street should not exceed 500 feet, or 1,000 feet where there are unusual conditions; the diameter of the cul-de-sac should be 90 feet and it should be paved; and the grade should not exceed five percent.

From PAS Memo, APA, November 1985

[1] This is the same standard given in Site Planning Standards, Planning Design Criteria, and Control of Land Subdivision.

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