Regulatory signs

A number of regulatory signs are appropriate for roundabouts and are described below.

YIELD sign

A YIELD sign (R1-2), shown in Exhibit 7-1, is required at the entrance to the roundabout. For single-lane approaches, one YIELD sign placed on the right side is sufficient, although a second YIELD sign mounted in the splitter island on the left side of the approach may be used. For approaches with more than one lane, the designer should place YIELD signs on both the left and right sides of the approach. This practice is consistent with the recommendations of the MUTCD on the location of STOP and YIELD signs on single-lane and multilane approaches (MUTCD, §2B-9). To prevent circulating vehicles from yielding unnecessarily, the face of the yield sign should not be visible from the circulatory roadway. YIELD signs may also be used at the entrance to crosswalks on both the entry and exit legs of an approach. However, the designer should not use both YIELD signs and Pedestrian Crossing signs (see Section 7.1.3.5) to mark a pedestrian crossing, as the yield signs at the roundabout entrance may be obscured.

ONE WAY sign

ONE WAY signs (R6-1R) may be used in the central island opposite the entrances. An example is shown in Exhibit 7-2. The ONE WAY sign may be supplemented with chevron signs to emphasize the direction of travel within the circulatory roadway.

At roundabouts with one-way streets on one or more approaches, the use of a regulatory ONE WAY sign may be confusing. In these cases, a Large Arrow warning sign may be used.

KEEP RIGHT sign

KEEP RIGHT signs (R4-7 or text variations R4-7a and R4-7b) should be used at the nose of all nonmountable splitter islands. This sign is shown in exhibit 7-3.

For small splitter islands, a Type 1 object marker may be substituted for the KEEP RIGHT sign. This may reduce sign clutter and improve the visibility of the YIELD sign.

Lane-use control signs

For roundabouts with multiple entry lanes, it can often be confusing for unfamiliar drivers to know which lanes to use for the various left, through, and right movements. There is no international consensus on the effectiveness of lane-use signs and/or pavement markings.

The designation of lanes on entry to a roundabout is directly related to a number of factors:

• Traffic volume balance. Roundabouts with especially heavy left- or right-turning traffic may require more than one lane to handle the expected demand (see Chapter 4).
• Exit lane requirements. In general, the number of exit lanes provided should be the minimum required to handle the expected exit volume. This may not correspond with the number of entry lanes on the opposite side of the roundabout that would use the exit as through vehicles (see Chapter 4).
• The rules of the road. Drivers have a reasonable expectation that multiple through lanes entering a roundabout will have an equal number of receiving lanes on exit on the far side of the roundabout (see Chapter 2).

Lane-use control signs are generally not required where the number of receiving lanes for through vehicles on exit matches the number of entry lanes, as shown in Exhibit 7-4. Lane-use control signs should be used only for the following conditions:

• Where only a single exit lane is provided to receive two lanes of vehicles making through movements, lane-use designations should be made to indicate that an entry lane drops as a turning movement (see Exhibit 7-4). This does not include cases where an approach is flared from one to two lanes at the roundabout.
• Where left- or right-turning traffic demand dictates the need for more than one left-turn lane or more than one right-turn lane for capacity reasons (see Exhibit 7-5).

The use of a left-turn-only lane designation as shown in the exhibits may be initially confusing to drivers. This type of designation has worked successfully in other countries, and there is no evidence to suggest that it will not work in the United States. However, given the general unfamiliarity of roundabouts to drivers in the United States at this time, it is recommended that double-lane roundabouts be designed to avoid the use of lane-use control signs wherever possible, at least until drivers become more accustomed to driving roundabouts.