Increasingly, high-occupancy vehicle (HOV) lanes are being called into question. Transportation researchers find them to be of limited value in relieving congestion, and elected officials are under increasing pressure to convert these limited-access lanes into general-purpose lanes. But a number of metro areas are experimenting with a different alternative: opening up these limited-access lanes to paying customers.
The new approach is called high-occupancy/toll (HOT) lanes. As of early 1999, two such projects are in operation in California and another in Texas. Because they give motorists a choice between (1) continuing to use general-purpose lanes at no direct charge and (2) using express lanes at a specific, direct price, HOT lanes are an example of “value pricing” (charging a price only for a higher level of service).
There are at least four circumstances under which the HOT lane approach may be applicable:
- If an existing HOV-2 lane is seriously underutilized, converting it to a HOT lane makes use of this excess capacity.
- If an existing HOV-2 lane becomes congested and is set to be converted to HOV-3, experience shows that this change will lead to a large amount of excess capacity; this is also an opportunity to sell the excess, by converting to HOT.
- When an existing congested freeway is programmed for capacity expansion, the addition of a HOT lane in either direction may offer more benefits than adding either a conventional HOV lane or a generalpurpose lane.
- When a new freeway is to be built, it can be built with fewer lanes if a value-pricing/HOT lane concept is employed to limit demand during peak hours.
Legal authority for such HOT-lane projects is provided at the federal level by the Value-Pricing program included by Congress in the 1998 TEA-21 legislation. State legislation may be needed, for one or more of the following: (1) to permit conversion of existing HOV lanes to HOT lanes, (2) to permit charging a fee to use a state highway, and (3) to permit enforcement via video and electronic means.
New technology-in particular non-stop electronic toll collection using windshield-mounted transponder tags-makes HOT lanes feasible without the need for toll booths or toll plazas. HOT lanes can be separated from regular lanes simply by pavement striping and plastic pylons. Electronic and video technology can assist with enforcement.
In most cases the conversion of an existing HOV lane to a HOT lane should be more than self-supporting from the new toll revenues. In certain cases, the addition of a HOT lane, at grade, may also be selfsupporting, if no major interchanges need to be rebuilt. Public-private partnerships may make such projects easier for public agencies to carry out.
Public officials’ greatest concern may be the political feasibility of HOT lanes. Experience to date shows that, once in use, a HOT lane benefits both users and non-users, becoming quite popular. As long as carpools and buses continue to have good access, the lanes will continue to serve their HOV function. Some environmental groups actively support HOT lanes, realizing that value pricing-by smoothing traffic flow- reduces running emissions compared with stop-and-go driving. Experience also shows that drivers of all income levels make use of HOT lanes at those times when they really need to get somewhere on time; they are not used solely by the affluent.