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Improving highway advisory radio predictability and performance
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2011-01-01
[PDF-9.58 MB]
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Abstract:Highway Advisory Radio (HAR) stations, sometimes referred to as Travelers’ Information Stations (TIS),
allow highway agencies to broadcast important messages about traffic, weather and roadway conditions to
motorists. Caltrans has deployed HAR stations across the state, but performance is often unpredictable,
with signal strength often failing to meet the state’s intended design criteria.
Caltrans sought to better understand the underlying design factors involved with HAR signal
transmission. The agency wanted to know what research, guidelines, specifications or practices among
other agencies were available to improve the design and deployment of HAR stations. Caltrans’ ultimate
goal is to achieve more uniform and predictable signal strength and quality.
This Preliminary Investigation is limited in scope to AM band HAR stations and is focused on design
factors related to radio wave propagation; topography; environmental characteristics (geology, ground
conductivity); relevant system components and configurations (antennae, grounding); and related factors
affecting HAR performance.
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