Cornell Local Roads Program

Riding the Rails...

Let’s start with a basic idea: Guiderail is a roadside hazard. In New York State, it is the third most common item struck in “run off the road” collisions, after utility poles and trees. While guiderail can protect the public from fixed hazards, steep slopes and ditches, it needs to be placed carefully and should only be used after a thorough review of all the options available to reduce the hazard.

Crashed automobile impaled on a guiderail

A simple five-step review can help determine the best way to protect the traveling public. Keep in mind that cost is always a factor. An expensive solution that will provide little benefit may not be justified. On the other hand, think about how your town or department might be affected if an accident occurred.

Remember that you need to maintain the guiderail. If you cannot afford to maintain it, should you even install it? This is especially important from a liability standpoint: you had reason to believe there was a serioushazard or you would not have placed the guiderail. If you do not maintain the rail, then you have failed to adequately protect against a hazard.

  1. Remove the Hazard
    Obviously, the best solution is to remove a hazard. Cut down and remove dangerous trees (get permission first). Keep ditches traversable. If a slope is flatter than 1 on 3, a vehicle can safely traverse the slope and there is no need for guiderail. However, if the backslope is steep or there is something dangerous on the slope, such as a tree which cannot also be removed, the hazard remains.
  2. Relocate the Hazard
    If a hazard cannot be removed, perhaps it can be relocated to a less dangerous place. A utility pole in a steep-sided ditch is very likely to be struck. Moving utility poles to the inside of corners or to the top of slopes makes them less of a hazard
  3. Make the Feature Crashworthy or Traversable
    Not all hazards can be removed or relocated. Signs and light poles are common examples. In those cases, providing breakaway hardware can make them safer. If slopes and ditches cannot be made completely traversable, flatten them as much as possible. Culvert ends can be shielded. Rebar and other sloped grates can allow vehicles to travel over the end of a culvert with little damage to either the vehicle or the culvert itself. This can also help in maintenance since some mowers may be able to travel over these grated end sections. Make sure any grates do not interfere with the function of the culverts or create additional hazards themselves.
  4. Shield the Hazard
    This is where the choice is made for or against guiderail. If a guiderail will not actually improve safety, other alternatives may be better. Remember, guiderail is itself a roadside hazard. Also, placing guiderail at one location may increase the risk to the municipality if there are other locations with a greater potential hazard and guiderail is NOT installed. Before placing any guiderail, look over your entire roadway inventory and decide if this is the most critical location. A long-term plan of where, when and how to place guiderail and otherwise improve your overall roadway and roadside safety should be developed.
  5. Delineate the Hazard
    Finally, if none of the above steps are possible or economically feasible, delineate the hazard. Delineation is the last option you should use, not the first. If used, it is especially valuable at night, and for potential hazards that drivers cannot readily see, such as culverts. If delineation is chosen, you must document why the other alternatives were not used. If you cannot show why all of the other options were not possible, then you should be looking at something other than delineation.

Once you have thoroughly examined all the options and made a decision to use guiderail, be sure to place, install and maintain it properly. There is very good, free information available to help in the design and placement of guiderail.

A table (PDF), available for download, shows some basic information on the common types of guiderail used in New York State.


Roadway Safety Fundamentals (PDF), Cornell Local Roads Program

Highway Design Manual, New York State Department of Transportation.

Guide Rail Quick Reference Sheets, NYSDOT

CLRP Tech Tips:
Guiderail (4 topics)

The information in the table on the next page is from the sources listed above. This is a simplified version of the full Guide Rail Sheet provided by NYSDOT. The full version contains information on standards, pay item numbers and where to obtain detailed design information on guiderail runs, transitions and end sections. Anyone who does a lot of guiderail design or layout may want to obtain the full sheet.

Thanks to Terry Hale, NYSDOT, for review and help with the simplified sheet.

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This work by the Cornell Local Roads Program (CLRP) is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 Unported License.