​Traveler information systems have been developed to distribute real-time traffic, roadway conditions, weather and other related traveler information to drivers through vehicles, PDAs, kiosks and websites. Providing this information, travelers can make route and timing decisions before or during their trip. On July 21, 2000, the Federal Communications Commission assigned 511 as the nationwide traveler information telephone number and granted responsibility for it to government transportation agencies. Since that time, several statewide and regional 511 systems have been implemented throughout the United States.

References

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​FHWA 511
Simply stated, 511 is an easy-to-remember 3-digit telephone number, available nationwide, that provides current information about travel conditions, allowing travelers to make better choices - choice of time, choice of mode of transportation, choice of route.
FHWA 511

Developing Traveler Information Systems Using the National ITS Architecture
This is one of a series of documents providing support for deploying Intelligent Transportation Systems (ITS). This series addresses Traffic Signal Control Systems, Freeway and Incident Management Systems, Transit Management Systems and Traveler Information Systems.
Developing Traveler Information Systems Using the National ITS Architecture

Weather Information for Surface Transportation
In many cases, weather information helps travelers determine when to take a trip, which route, or whether to go at all. When weather turns sever, it can not only change daily travel habits, it can also be deadly.
Weather Information for Surface Transportation