Traffic Management > En-route Traveler Info > Highway Advisory Radio

Highway Advisory Radio (HAR) was first used in 1940 on the George Washington Bridge in New York.  The Federal Highway Administration began researching HAR in 1971, sponsoring several successful studies and field implementations.  By the mid to late 1970âs, HAR installations existed in Pennsylvania, Colorado, Minnesota, Wyoming, and Iowa.  Further FHWA research was conducted in the early 1980âs to determine the optimal message length, style, presentation, and repetition rate. 

The use of HAR has expanded considerably, and now plays an important role in Advanced Traveler Information Systems, typically providing the following information: 

• Current traffic conditions
• Travel restrictions
• Notices of events
• Directions to popular tourist attractions
• General safety information

HAR has an inherent advantage over commercial radio traffic broadcasts in that commercial radio stations do not broadcast continuous traffic information-even during peak periods. Also, because of its limited range, the information is more likely to be relevant to the listener. A typical HAR system has two subsystems- a transmission system and a system of Variable Message Signs (VMS) or static signage advising motorists to tune in to the HAR station. Installation costs depend on the type of equipment, and can reach $30,000 to $40,000 per installation (Source: Caltrans). 

To broadcast messages, HAR systems typically use either 10-watt transmission or low-power transmission (0.1-watt). When properly installed, 10-watt transmitters have a broadcast radius of about 3 to 6 miles.  FCC licensing is required, and broadcast is permitted between 453 kHz and 1710 kHz. The 10-watt HAR zone of influence is radial and adjoining transmission zones typically interfere with each other at their interfaces.  Special FCC waivers can be obtained for the use of superstations that equip 10-watt transmitters with a high efficiency antenna to extend the coverage range to a 10 to 15 mile radius. 

The other HAR installations utilize a series of low-power, 0.1 watt transmitters which are interconnected and synchronized to form a zone of coverage.  Low-power transmission does not require FCC licensing and can be broadcast over any unused commercial radio frequency.    The major advantage of low power transmission over 10-watt transmission is that transmitters can be arranged in a customized zonal configuration, allowing unique messages to be broadcast in each zone as opposed to the 10-watt transmitters which broadcast radially outward. 

Antenna systems for HAR are typically  vertical monopole antenna or cable antenna. Vertical monopole antennas are more commonly used and can generate signals which are intelligible from 3 to 8 miles, depending on the type of transmitter used.  Cable antennas are either buried or hung along the roadway and consist of two main types: radiating and "leaky". Radiating cable antennas are restricted to 1.86 mile runs over which the message is heard. The so called "leaky" cable antennas, unrestricted in length, radiate a weak signal just strong enough to be detected along the length of the cable. The primary advantage of cable antennas over vertical antennas is that in areas where the signal is weak, such as in tunnels, cable antennas can be used within the tunnel to broadcast messages (for example, the Channel Tunnel uses radiating cable antennas).  The primary disadvantage of cable antennas are that maintenance and installation (trenching) costs are considerable.  Furthermore, cable antennas are susceptible to disconnects due to construction activity and corrosion by water.  See our Telecommunications Diagram on HAR for more information.

Public/Private Partnerships in HAR
In early 1998, TIRN Broadcasting, Inc. and the Florida DOT will jointly unveil an emerging Florida Traveler Information Radio Network (TIRN). As a contractor to the Florida Department of Transportation, TIRN Broadcasting will provide a completely dedicated radio network comprising 19 commercial radio stations covering the state of Florida. TIRN is unlike any existing HAR application in the United States due to the public/private partnership as well as the projected coverage area: the entire state of Florida. 

The following agreement between FDOT and TIRN Broadcasting was reached: 

• FDOT will provide right-of-way access for up to 4600 new roadway signs to be constructed within the ROW of limited access highways throughout the state, including the Florida Turnpike and major expressways. These 6 by 6 1/2 feet signs will advertise the radio network to millions of annual out-of-state and out-of-country visitors by displaying the appropriate frequency.
• TIRN Broadcasting is responsible for purchasing and installing the signs.
• FDOT will routinely get one minute in each ten for messages to travelers, and the right to completely take over the network to alert travelers if there are major accidents or pending natural disasters.
• TIRN Broadcasting can sell four minutes of advertising in each ten-minute period.
• After 18 months, TIRN Broadcasting and the Florida Department of Transportation will re-negotiate the contract. The new contract might require TIRN to pay a fee to the FDOT, depending on whether or not a profit is made.

TIRN'S total investment for the initial deployment of about 2,000 signs was about $9 million, not counting the 19 radio stations, which will amount to another $25 or $26 million in radio station assets that are committed to this concept and project. 
 

Benefits

Minnesota

The Human Factors Research Laboratory at the University of Minnesota conducted an evaluation in 1994 of a HAR system providing real-time information to drivers in cars equipped with a radio receiver that incorporates special features. A digital channel was added to the regular FM signal as a digital sideband that carried the current traffic information received by a special in-vehicle "Delco" receiver.  The Delco device looks like a typical car radio system but with a modified scrolling text display with two lines of eight characters each.  The results of the evaluation of safety, performance and public perception of the device are as follows: 

• The device was difficult to understand and to operate correctly.
• Regional messages could be interpreted as current local traffic information since the Delco receiver was capable of transmitting data accurately over a large metropolitan area.
• The Delco receiver degraded driving performance compared to driving without using the receiver. Performance was based on factors such as lane drift, acceleration/deceleration changes, speed maintenance, braking and other typical driving tasks.
• Participants were not convinced that these systems provided better information than what is available by listening to traffic announcements on their conventional car radios.
• Problems with the design of the software used in the control room for the assembly of traffic messages included data prioritization so that the most frequently entered data were on the top of the list.
• There was a need for human factors improvements to the information delivery system at the TMC's control room.

Source: Human Factors Evaluation of the Delco RDS Radio Receiver and the RDS Architecture, by Max Burrus, et al. (University of Minnesota, Human Factors Research Laboratory, 141 Mariucci Arena Operations, 1901 4th St., SE, Minneapolis, MN 55455) (August 1994) [TD100:MN95-01] 

In 1995, the Minnesota DOT conducted a survey of 300 drivers who use the freeways in the metro area during morning rush hours in order to determine the traffic information needs of these drivers. The intent was to help Minnesota DOT measure its current radio broadcast effectiveness and provide input for future planning. The survey responses are as follows: 

• Over 80 percent claim they have taken an alternative route as a result of a traffic report and only 2 percent did not know about traffic reports on various radio stations;
• Current radio broadcasts of traffic information were rated as being "very useful";
• Commercial radio station reporting continuous traffic conditions was preferred.
• Electronic signs, or VMS, on freeways alerting motorists to problems ahead were highly rated by respondents.
• Ideas that required more effort or disrupted routines (e.g., phone numbers to call or cable TV programs to watch at home before leaving) were not highly rated.
• The more important information relates to blocked or unduly slowed down lanes and to poor road conditions due to weather as opposed to information such as parking availability.

Source: Motorist Information Study for Minnesota Department of Transportation (Carmichael Lynch, 800 Hennepin Ave., Minneapolis, MN 55403) (Aug-Sept. 1995) [TD 100: MN 95-950801] 

Virginia

The Virginia Department of Transportation (VDOT) has deployed HAR in several regions of Virginia.  In 1995, the Virginia Transportation Research Council (VTRC) began a study that reviewed previous research, examined the use of HAR in Virginia, and surveyed Virginia motorists to ascertain the public's perception of HAR.  The results of this study were used to develop a set of Operational Guidelines.  The Council concluded that: 

• Proper HAR operation is personnel-intensive. Updating broadcasts with information of value to motorists takes time.  Linking isolated HAR transmitter units into a coherent traveler information system requires a concerted effort to consolidate information between multiple agencies.
• Motorists want specific, up-to-date information on congestion and incidents that affect their travel.  Situations that can be communicated with other traffic control devices or that do not affect motorists do not warrant HAR broadcasts.
• Motorists are not turning to HAR broadcasts.  Many motorists do not understand when they are in an HAR broadcast area, and what information HAR offers them.
• Motorists currently get most of their traffic information from commercial radio traffic reports. VDOT does not have the resources to provide the level of information provided by commercial radio stations.
• Variable Message Signs (VMS) offer considerable advantage as advisory signing for HAR.  Static HAR advisory signs offer a single, inflexible attention statement to drivers.  Flashing beacon signs face the same problem, and are confusing to some motorists. VMSs can alleviate these problems, directing the message to the appropriate audience.
• Vertical monopole antennas are more cost-effective than cable antenna systems.

Source: An Investigation of Operational Procedures for Highway Advisory Radio System by Brain Smith et al. Virginia Transportation Research Council, 520 Edgemont Rd., Charlottesville, VA 22903-0817. Sept. 1995. 

Author: Joe Wanat. Last update: 2/12/98