AASHTO defines control of access as “a condition where the right or owners or occupants of abutting land, or other persons, to access in connection with a (highway)1 street is fully or partially controlled by public authority.” Full control of access gives preference to through traffic by providing access connections with selected public roads only, and by prohibiting crossings at grade or direct private driveway connections. Partial control of access gives preference to through traffic to a degree that, in addition to access connections with selected public roads, there may be some crossings at grade and some private driveway connections.
E 362.1 Types of Access Control Devices
Freeways are examples of fully controlled access highways. By the very nature of City streets, provisions must be made for access to abutting property. This means that the City’s main concern is with partial or limited access control of streets.
E 362.11 Frontage Roads
When a fully controlled freeway or partially controlled (highway)1 street is developed through the City, some existing intersecting streets must be cut off to prevent promiscuous access to these main arteries. It is uneconomical to provide grade-separate crossings or to leave many dead-end streets. One method is to provide a new street or make use of an existing street that parallels the freeway or highway to connect all or some of the cut-off streets. New subdivisions abutting main highways are also required to provide a frontage road as a means of access control.
In addition to access control, a frontage road provides circulatory movements for local or subdivision traffic. It provides continued access to the abutting residential, industrial, or commercial properties remaining. It provides, for short distances, an alternate route parallel to the main highway or freeway. Its chief function, however, is to keep local traffic isolated from the main highway except at predesignated access points.
The alignment and grade determination of the frontage roads are treated in the same manner as those of most other city streets. Design problems encountered will be covered elsewhere in this Part of the Manual.
E 362.12 Cul-de-Sacs and Dead-End Streets
Cul-de-sacs and dead-end streets are local streets terminated or closed at one end. Turnaround provisions are included at the ends of cul-de-sacs, but not in dead-end streets. Cul-de-sacs are used frequently in new subdivisions, or they may result from the development of freeways or partially controlled highways at points where access is controlled without frontage roads. Where a minor street is cut off so that it neither crosses the arterial route nor enters it, a cul-de-sac or a dead-end result. Dead-ends are used where existing improvements do not permit turnaround provisions from an economic or a design standpoint.
There are several advantages in cutting off access to a street. Normally a street, no matter how unimportant, is used by some traffic not destined for or originating in that block. Such traffic is eliminated entirely on a dead-end street, increasing the street value for residential purposes because of decreased noise and odor and increased safety.
Where an existing street is commercial in character, there are objections to dead-ending in that the commercial establishments are not readily accessible. This can have a depressing effect on some businesses (as in the case of gas stations). Rarely are commercial streets dead-ended.
Damage sometimes results from terminating streets, and an element of extra cost may be involved. Consideration should be given to possibilities for connecting two or more adjacent streets as an alternative to dead-ending them, to avoid possible damage and improve local circulation.
Other uses of cul-de-sacs, design of alignments, grades, and other related matters will be discussed in Section E 520 of this Manual.
E 362.13 Alleys.
Areas zoned for industry, commerce, and multiple residences are usually subject to heavy vehicular use. Where this type of property abuts a major or a secondary (highway)1 street, the heavy flow of traffic generated in this area can sometimes create a complex traffic problem. Not only is vehicular access to the property impeded, but vehicle movement along the major and secondary (highway)1 street is seriously restricted.
A solution, or at least a partial solution, sometimes lies in providing some means of access control. In this regard, in addition to its other uses, an alley, where properly located, may serve as a means of access control. The access control is generally accomplished by denying ingress to and egress from the major or secondary (highway)1 street to the abutting property. The alley is located at the rear of the property and provides vehicular access to the intersecting local streets. Off-street parking, residential driveways, delivery service, and garbage trucks are handled in this manner. This type of access control eliminates points of conflict where vehicles enter a heavily congested street other than at an intersection. It also leaves lanes that would otherwise be used for parking, loading, etc., open for through traffic.
Alley design is dealt with in Section E 510 of this Street Design Manual.
Footnotes
- The text in parenthesis is from the legacy Street Design Manual text and has been superseded by the italicized text that follows.
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