Medians are generally outlined by either painted strips, raised pavement markers, or mountable or barrier type concrete curbs. Each type has specific uses, advantages, and disadvantages. Special or individual problems may be solved by combining types to make use of the advantages and eliminate the disadvantageous characteristics of each type.
E 662.1 Painted Medians or Pavement Markers
Areas reserved for the median strips may be outlined by means of a reflectorized type of painted stripe or raised pavement markers. Striping is generally painted directly on the pavement surface. This type of median is normally installed by the Department of Transportation and is the one most widely used in City streets.
E 662.11 Advantages
Painted stripes or markers are the most economical from both a construction and a maintenance standpoint. Emergency and disabled vehicles have easy access for painted or marked median as a moving lane or for temporary storage. Many changes in the painted outline are necessary, it is simply a matter of sandblasting or removing the existing stripes or markers and restriping or remarking in the new location.
E 662.12 Disadvantages
The main disadvantage of a painted median is that it does not offer any physical restraint to vehicular crossing, and consequently does not adequately protect pedestrians, traffic signals, or signs located in the strip area. On rainy nights the painted lines are difficult to see.
E 662.2 Curbed Medians
Median strips may be outlined by construction of raised barriers or mountable type of concrete curbs. Barrier curbs for curbed medians should normally be Type “C” Integral Concrete Curb with 1-foot-wide concrete gutter. Normally, the structural, grade, and geometric aspects of median design are handled by the Bureau of Engineering with the Department of Transportation supplying traffic data and acting in an advisory capacity.
E 662.21 Advantages
Where left tums are prohibited, or where other facilities may attract illegal left turns, the barrier type curb is used. This prohibits crossings at other than predesigned locations. The deflective action of such a curb helps prevent collision of vehicles with piers, traffic signals, or other structures that may be constructed on the median strip area. It acts as a more positive barrier or buffer between opposing lanes of traffic. It may be used to separate the roadways so that they may be designed with a relative degree of independence of each other.
E 662.22 Disadvantages
Medians with barrier type curbs are not readily accessible to emergency or disabled vehicles. The cost of their construction and maintenance may be higher. Any changes in a curbed median layout are more expensive than those in the painted or marker type median. Curb acts as a barrier for drainage and sometimes creates drainage disposal problems. Although the deflecting action of raised barrier curbs decreases opposing traffic accidents, it tends to increase accidents between vehicles on adjacent lanes moving in the same direction.
E 662.3 Mountable Curbed Medians
When barrier type curbs are called for in front of hospitals, fire and police stations, or any other institutions used by emergency vehicles, the mountable type of curb is generally used. Whenever a mountable curb is required on medians, the first 12 feet back from the nose should be vertical barrier type curb followed by a 20-foot-length transition to the sloping mountable curb. The main purpose of mountable curb, of course, is to maintain traversability and still discourage unauthorized vehicles from making illegal crossings.
Mountable curbs are an attempt at a compromise between barrier and painted medians. They overcome only to a small degree the disadvantages of the other two types. They are traversable, and therefore are not as effective a barrier between opposing traffic lanes, nor do they completely discourage indiscriminate vehicular median crossings. They do not effectively protect traffic signs, etc., mounted on the median. They are more costly to construct or relocate than painted stripes, and they also create drainage problems, as do barrier curbs.
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