Difference between revisions of "Category:240 Maintenance and Emergency Crossovers"

Maintenance and emergency crossovers may be constructed on freeways and expressways so that maintenance, emergency and law enforcement vehicles can avoid extremely adverse distances. These crossovers

• facilitate maintenance activities such as snow removal and
• provide ample access for law enforcement or emergency medical services responding to roadway incidents.

Maintenance crossovers may be needed at one or both ends of interchange facilities, depending on the type of interchange.

Public at-grade intersections or crossovers are not constructed on fully controlled access routes. Median openings are considered at intervals outlined in 940.7 Median Opening Spacing on other routes.

The Federal Highway Administration must approve maintenance and emergency crossovers on interstates. The State Maintenance Engineer must approve maintenance and emergency crossovers on all other state routes.

240.1 Location

When selecting a location for a maintenance and emergency crossover, the guidance contained in AASHTO’s A Policy on Geometric Design of Highways and Streets should be used in addition to the following general guidelines:

1. Maintenance and emergency crossovers should not be located closer than 1,500 ft. to the end of a speed-change ramp or to any structures such as bridge columns or guardrail located in the median.

2. Maintenance and emergency crossovers should be located only where the Design Entering Sight Distance is provided.

3. Maintenance and emergency crossovers should not be located within curves requiring superelevation.

4. Spacing of crossovers should be every 2.5 miles, and

5. Interchanges that are closer than 2.5 miles apart should not have maintenance and emergency crossovers unless a defined need exists for maintenance, emergency, medical or law enforcement purposes.

240.2 Request for Crossover by Maintenance Personnel

The following information is required when submitting a request to construct a new maintenance and emergency crossover on an existing route:

1. A letter of transmittal to the State Maintenance Engineer stating the route, county and exact station number of the proposed crossover. The request should contain a general statement regarding the need for the crossover, the sight distance in both directions of the proposed crossover, the effect on the median drainage and a statement that the crossover changes are acceptable to the local emergency responders.

2. A general county highway map showing the location of the proposed crossover and all existing crossovers and interchanges within 5 miles on either side of the proposed crossover.

3. A copy of the plan-profile sheet for the section of roadway where the proposed crossover will be located.

240.3 Maintenance and Emergency Crossover Construction Requirements

1. Crossovers shall be constructed with an aggregate surface no wider than 20 ft. and with turning radii of not more than 10 ft.

2. To be inconspicuous to mainline traffic, the surface should be depressed below shoulder level.

3. Sideslopes should be constructed 1V:10H or flatter to minimize their effect as obstacles to uncontrolled vehicles that may enter the median.

4. If possible, the crossover should be located where a pipe is not necessary. All drainage structures constructed in the median must be built to current safety standards. Refer to Standard Plan 606.41 for drainage piping plans and pipe end treatment options.

5. The surface shall not be upgraded to a higher type surface.

6. Crossovers are to be in good repair at all times.

7. Signing for a maintenance and emergency crossover shall be in accordance with 903.5.53 AUTHORIZED AND EMERGENCY VEHICLES ONLY.

240.4 Guard Cable Termination at Emergency Crossovers

The design for guard cable termination as well as the grading for the crossover should be in accordance with Standard Plan 606.41, Sheet 6 of 6. The width of the crossover should not exceed 20 ft. If feasible, the crossover should be located immediately downstream of an existing median drop inlet in order to eliminate a pipe culvert.

An unauthorized U-turn into high-speed traffic, on the part of the general public, represents a hazardous situation. In order to discourage non-emergency use of the crossover by motorists at large, the crossovers should be kept narrow with small transition radii. Neither should they have hard surfaces or deceleration tapers.

A 6 in. aggregate surface of predominately larger material should provide an adequate, all-weather surface that still appears unattractive to the non-emergency motorist.

Access Justification. The FHWA requires justification of access for each new freeway access designed. Their approval is granted in response to an Access Justification Report (AJR). The AJR details the purpose and need for the access and analyzes its impact upon traffic flow. As the AJR is typically a rather lengthy and time consuming document to produce, the FHWA should enter into a programmatic AJR with MoDOT.

The parameters of emergency median crossovers as well as their impact upon traffic are both predictable and static. As such, a single AJR could efficiently address the design and construction of every future emergency access.