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Section 4: Frontage Roads

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Overview

Table 4-4: 3R Design Guidelines for Rural Frontage Roads and Table 4-5: 3R Design Guidelines for Urban Frontage Roads show geometric design guidelines for 3R projects on rural and urban freeway frontage roads. These guidelines are acceptable for those projects involving either rehabilitation of only the frontage road or rehabilitation of the frontage road in conjunction with rehabilitation of the freeway mainlanes. It is not the intent of these 3R frontage road design guidelines to be used when a freeway section is reconstructed from right of way line to right of way line even though no additional frontage road lanes are added. Complete frontage road reconstruction projects should reference the applicable reconstruction guidelines for the appropriate criteria.

Frontage roads are built in some locations initially in a phased construction sequence with the mainlanes to be built when traffic conditions warrant. If the frontage road is serving as the principal roadway pending future mainlane construction, the 3R design guidelines for rural multilane highways would be applicable for rehabilitation work on these facilities.

Anchor: #CHDEFAADTable 4-4: 3R Design Guidelines for Rural Frontage Roadsa

(US Customary)

Design Element

Current Average Daily Traffic

-

0 - 1500

1500 or more

Design Speed

30 mph

40 mph

Lane Width

10 ft

11 ft

Shoulder Width

Two-Way Operation

1 ft

3 ft

Inside Shoulder Width

One-Way Operation

1 ft

2 ft

Outside Shoulder Width

One-Way Operation

1 ft

4 ft

Horizontal Clearance

7 ft

16 ft

Bridgesb: Width to be retained

22 ft

24 ftc

a These values are intended for use on rehabilitation projects. However, the designer may select higher values to provide consistency with adjoining roadway sections, to provide consistency with prevailing conditions on similar roadways in the area, or to provide operational improvements at specific locations.

b Where structures are to be modified, bridges should meet approach roadway width as a minimum. (Approach roadway width is the total width of the lanes and shoulders.) Greater bridge widths may be appropriate if the rehabilitation project increases roadway life significantly or if higher design values are selected for the remainder of the project. Existing structure widths less than those shown may be retained if the total lane width is not reduced across or in the vicinity of the structure.

c For current ADT exceeding 2000, minimum width of bridge to be retained is 28 ft.



NOTE: Online users can view the metric version of this table in PDF format.

Anchor: #CHDHHEEJTable 4-5: 3R Design Guidelines for Urban Frontage Roadsa

(US Customary)

Design Element

All Traffic Volumes

Design Speed

30 mph

Lane Width

10 ft

Shoulder Width

0 ft inside

2 ft outside

Horizontal Clearance

Back of curb or edge of shoulder

Curb Offset

1 ft either side

Bridges: Width to be retained

Approach roadway not including shoulders

a These values are intended for use on rehabilitation projects. However, the designer may select higher values to provide consistency with adjoining roadway sections, to provide consistency with prevailing conditions on similar roadways in the area, or to provide operational improvements at specific locations.



NOTE: Online users can view the metric version of this table in PDF format.

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