I've found very little on crash investigation sites, and the descriptions of it pretty much are the same as a rest area on any freeway (except maybe smaller since it has room for about five cars only). I think "áreas de descanso" would be understood, although I did find "de servicio y descanso" as well.

http://www.dot.wisconsin.gov/travel/stoc/crashsites.htm

http://www.us41wisconsin.gov/remos_downloads/Crash investiga...

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Note added at 2 hrs (2010-05-14 17:08:19 GMT)
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Crash investigation sites

Crash investigation sites are designated safe zones for distressed motorists to relocate to if they are involved in an incident on the freeway.

The sites are intended for use by motorists to exchange insurance information or make emergency repairs to vehicles following a minor collision or breakdown, provided that the vehicle is able to be driven. They are also used as relocation sites by freeway service patrols.

The shoulder of the freeway is not a safe place for motorists to stop. These sites enhance safety by moving pedestrians and stalled vehicles away from high-speed, "live" traffic lanes. They also remove distractions and potential obstacles for other motorists, thereby minimizing secondary incidents.

Most crash investigation sites are located near freeway exits, but are not visible from the freeway. Future plans include sites along freeway off-ramps for easier accessibility.



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Note added at 2 hrs (2010-05-14 17:09:25 GMT)
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Crash Investigation Sites (CIS)
7.1. Introduction and Usage
The idea of "crash investigation sites" or areas outside of the freeway mainline where
investigations or minor vehicle repairs are made is an attempt to minimize the exposure to
personal harm and the danger of causing additional incidents on the system. Crash
investigation sites (CIS) are specially designated and signed areas off the mainline where
motorists, law enforcement, and other public service vehicles can be temporarily located. The
sites provide an area to complete small vehicle repairs, hand out citations, or conduct crash
investigations. Typically these areas are well lit, safer than using a freeway lane or shoulders,
and provide enough storage area to hold up to five passenger vehicles.