programs is illustrated, and alternative strategies for building political support are outlined.

In the few instances when congestion pricing was proposed in the past, policy makers eschewed it, in part because of the perception that having queues of motorists at toll booths to pay congestion prices would be self-defeating. Advances in electronic toll collection technology, however, are rapidly overcoming this problem (Pietrzyk, Vol. 2; May, Vol. 2). Some toll roads in the United States and abroad are already offering electronic toll collection services. A wide variety of technologies is already in use to charge users automatically as they drive by a collection point. Regular patrons of toll roads can purchase inexpensive electronic tags, which are read by a computer that identifies the vehicle and debits the account of the patron with each use. The tag can be permanently mounted on the license plate or under the car, or placed inside the car on the dashboard; some tags are about the size of a standard credit card and about twice as thick. These electronic transactions can occur at speeds of 88 km/hr (55 mph) or more without delaying motorists (Pietryzk, Vol. 2; May, Vol. 2). Vendors claim that their technologies are over 99 percent accurate; existing technology, which is not as advanced as that to be introduced, has an operating reliability in the range of 93 to 98 percent (Pietrzyk, Vol. 2).

Relatively simple tags are of a “read only” design, in which the toll road authority computer reads the identity of the passing vehicle and debits that account with each use. If a prepayment method is used, the patron purchases a certain number of uses in advance, and his or her account is reduced with each use. In a postpayment method, the individual is simply billed. Most users of these systems handle their monthly transactions with a credit card. Privacy can be protected by handling prepayment transactions in cash. A “read/write” tag allows the authority computer to identify the patron and to record transactions on the patron's tag, which gives the patron an independent record of transactions to check against the authority 's billing. These tags are somewhat more sophisticated than those of the read-only design; they require a battery or a connection to the vehicle's battery. Purchases in cash to protect privacy would be somewhat inconvenient. In order to encourage the use of electronic toll collection, some toll