620.8 Islands
620.7.1 General (MUTCD Section 3G.01)
Support. This addresses the characteristics of islands as traffic-control devices. Criteria for the design of islands are set forth in At-Grade Intersections with Stop and Yield Control and At-Grade Intersections with Signal Control.
Standard. An island for traffic control purposes shall be the defined area between traffic lanes for control of vehicular movements or for pedestrian refuge. Within an intersection area, a median or an outer separation shall be an island.
Option. An island may be designated by pavement markings, channelizing devices, curbs, pavement edges, or other devices.
620.7.2 Approach-End Treatment (MUTCD Section 3G.02)
Guidance. The ends of islands first approached by traffic should be preceded by a gradually diverging marking on the roadway surface, to guide vehicles into desired paths of travel along the island edge.
Option. Approach-end markings that can be readily crossed even at considerable speed may contain slightly raised (usually less than 1 in. tall) sections of coarse aggregate or other suitable materials to create rumble sections that provide increased visibility of the marked areas and that produce an audible warning to road users traveling across them.
Standard. Rumble strips or other devices, when used in advance of islands having raised curbs, shall not be placed in such a manner as to constitute an unexpected obstacle.
Guidance. Bars or buttons should not project more than 1 to 3 in. above the pavement surface and should be designed so that any wheel encroachment within the area will be obvious to the vehicle operator, but will not result in loss of control of the vehicle.
Option. Bars or buttons may be preceded by rumble sections, or their height may be gradually increased as approached by traffic.
Pavement markings may be used with raised bars to better designate the island area.
620.7.3 Island Marking Application (MUTCD Section 3G.03)
Standard. Markings, as related to islands, shall consist only of pavement and curb markings, object markers, and delineators.
On the approach to islands, the triangular neutral area in advance of the end of the island shall include pavement markings as described in Approach Markings for Obstructions (MUTCD Section 3B.10).
Option. As indicated in Approach-End Treatment (MUTCD Section 3G.02), rumble sections, or other similar traffic control designs which contrast with the pavement surface, may also be applied in the triangular neutral area in advance of the end of an island.
Guidance. When raised bars or buttons are used in these neutral areas, they should be marked with white or yellow retroreflective materials, as determined by the direction or directions of travel they separate.
620.7.4 Island Marking Colors (MUTCD Section 3G.04)
Guidance. Islands outlined by curbs or pavement markings should be marked with retroreflective white or yellow material as determined by the direction or directions of travel they separate (see Colors (MUTCD Section 3A.04)).
Standard. Island curbs with non-mountable curbs at least 6 in. tall shall be marked with retroreflective markings or delineators.
The retroreflective area should be of sufficient length to denote the general alignment of the edge of the island along which vehicles travel, including the approach nose, when viewed from the approach to the island.
Option. On long islands, curb retroreflection may be discontinued such that it does not extend for the entire length of the curb, especially if the island is illuminated or marked with delineators or edge lines.
An island with mountable curbs less than 3 in. tall may be marked with retroreflective markings or delineators.
620.7.5 Island Object Markers (MUTCD Section 3G.05)
Option. Object markers may be installed alone or in combination with signs (such as KEEP RIGHT, KEEP LEFT, double arrows, or guide signs) located within the island.
620.7.6 Island Delineators (MUTCD Section 3G.06)
Standard. Delineators installed on islands shall be the same colors as the related edge lines except that, when facing wrong-way traffic, they shall be red (see Delineator Application (MUTCD Section 3D.03)).
Each roadway through an intersection shall be considered separately in positioning delineators to assure maximum effectiveness.
