Highway advisory radio

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To read about HAR in biology, see human accelerated regions.

A highway advisory radio sign in the United States

Highway advisory radio (HAR), sometimes also called travelers' information stations (TIS), are licensed low-power AM radio stations set up by local transport departments to provide bulletins to motorists and other travelers regarding traffic and other delays. These are often near highways and airports, and occasionally other tourism attractions such as national parks. In the latter case, they often provide a loop of prerecorded information about the park's historic and other background information.

These systems are licensed by the FCC in the United States under CFR Part 90.242 and are limited to a maximum signal of 2mV/m at 1.5km using a power of up to 10 watts to achieve this limit in the case of vertical antenna systems (the most common type). Up to 50 watts in the case of the radiating cable antenna systems may be used to achieve a maximum of 2mV/m at 60m from the radiating cable. Radiating cable systems are limited to a continuous antenna length of 1.9km. Cable systems are used for situations such as Dulles International Airport with very long limited-access approach roads where multiple systems can be placed in 1.9km segments. In some cases, such as LAX both radiating cable and antenna systems are employed as backup systems for one another.

Critical evacuation systems, such as those in the Florida Keys and near chemical and nuclear facilities, have been granted exceptional power waivers for emergency operations. These systems will typically operate under the normal power level, but have permission to exceed that limit, typically to 100w, in the face of a critical emergency evacuation situation.

The audible signal is required to include an audio low-pass filter which rolls off frequencies above 3kHz. Content is defined by the FCC as "noncommercial voice information pertaining to traffic and road conditions, traffic hazard and travel advisories, directions, availability of lodging, rest stops and service stations, and descriptions of local points of interest. It is not permissible to identify the commercial name of any business whose service may be available within or outside the coverage area of a Travelers' Information Station. However, to facilitate announcements concerning departures/arrivals and parking areas at air, train, and bus terminals, the trade name identification of carriers is permitted."

In the United States, only governments may have licenses for TIS/HAR stations, with some exceptions granted for quasi-governmental agencies and authorities. The FCC formerly reserved the bottom and top channels (530 and 1610) on the AM band for these stations, before the Extended AM broadcast band (1610 to 1700) was introduced in North America. Systems may currently be licensed on any frequency from 530-1700kHz. (Most radios tune to 1710; however, this does not seem to be used for any stations so far.) LPFM stations may be licensed to governments as well, but these are not considered part of the TIS/HAR service. Stations for U.S. national parks and other units under the U.S. federal government are licensed by the NTIA rather than the FCC.

1 LPFM
2 Outside of the United States
3 See also
4 External links

[edit] LPFM

In some states, LPFM stations are used to broadcast travelers information. Colorado has a statewide network of LPFMs used in this manner, while many other state, county, or local governments use one or more stations. Examples include WTUS-LP in Tuscaloosa, Alabama, operated by the Tuscaloosa Convention and Visitors Bureau; and WGEO-LP in Georgetown, South Carolina, which is operated by the Georgetown City Fire Department.

[edit] Outside of the United States

The concept is not limited to the US: TIS stations operate in Canada (on both AM and FM bands), in France (at 107.7 MHz FM along selected autoroutes), in Australia in some areas on 87.6-88 MHz FM, and possibly other countries as well.