In some situations, it is desirable to prohibit certain movements through the use of median or channelizing islands. Median islands can be used to separate inbound and outbound traffic. It is a curbed island which prevents egressing traffic from encroaching on the side of the drive used by ingress traffic. Channelizing islands further designate the correct turning path and define the merge area thus reducing conflicting movements. The geometry shall physically define the permitted movements and block the prohibited movements.
(a) Median islands (such as those illustrated in Figures 1 and 2)) shall be at least 4 feet wide -- with a maximum of 6 feet at the intersection. Median widths exceeding 6 feet are undesirable because they create turning problems, expand the intersection, and make it difficult to provide proper lane alignments with opposing existing or future driveways or roadways.
(b) Median islands shall be at least 25 feet in length.
(c) An island median shall be used to prevent encroachment on other driveway lanes whenever any combination of egress and ingress lanes exceeds three lanes.
(d) A median island shall be offset at least 12 feet from the edge of the traveled lane on the main road.
(e) The nose of a median island shall taper in height from 2” to 6” over a distance of 4 feet.
(f) Standard yellow edge lines shall be used at the divisional island. Also, white pavement markings shall be used to delineate traffic lanes when there are two or more lanes in the same direction. At high volume driveways, reflectorized pavement markers should be used to provide greater delineation.
(g) Channelizing islands shall be used on arterials and network collectors without a median where left turns are restricted and on one-way streets to discourage wrong way turns.
(h) Channelizing islands shall have a surface area of at least 75 square feet.
(i) All channelizing islands (such as those illustrated in Figures 3, 4, and 5) shall be offset at least 4 feet from the edge of the traveled lane to the face of curb or the width of the paved curbed shoulder whichever is greater on high-speed roadways or where the approach roadway is uncurbed. A mountable curb, no more than 4 inches high, should be used on the channelizing island if approach roadways are uncurbed.
(j) A turning radius of between 75 feet and 100 feet shall be used for channelizing islands in order to make it more difficult for a driver to make a maneuver which the design is intended to discourage. (Radii larger than 100 feet should not be used on egress unless an acceleration lane is provided because of the large angle a driver must rotate in order to see vehicles approaching from the left; the acceleration lane allows the driver to use the rear view mirror to select a gap).
(k) Figures 1 through 5 provide general design guidelines for median and channelizing islands. They primarily relate to commercial and industrial/retail driveways and they depict 90º T-type intersections. Applicable driveway widths and turning radii shall be determined based on the number and use of lanes on the driveway and the design vehicle chosen for the driveway. The depicted signage references the regulatory signs defined in the Ohio Manual of Uniform Traffic Control Devices (OMUTCD).
(Ord. 04-05. Passed 3-2-05.)