Patent ID: 8120512

Claim:
An apparatus comprising: first and second signposts that are supported at spaced locations, and that each transmit wireless signpost signals having a transmission range and containing a signpost identification, the signpost identification in signpost signals from said first signpost being different from the signpost identification in signpost signals from said second signpost; and structure defining spaced first and second paths of travel that are approximately parallel, said second signpost being disposed between said first and second paths of travel, said first path of travel passing through the transmission range of signpost signals from said first signpost and through the transmission range of signpost signals from said second signpost, said second path of travel passing through the transmission range of signpost signals from said second signpost, and said second path of travel being outside the transmission range of signpost signals from said first signpost; wherein said structure defines spaced first and second lanes for vehicles, said first and second paths of travel respectively extending along said first and second lanes, said first and second signposts being disposed on opposite sides of said first lane, wherein the transmission range of the first signpost is less than or equal to a width of the first lane and the transmission range of the second signpost is less than or equal to a width of the second lane.