Congestion charging mechanisms for
            roads : an evaluation of current practice
The author explores 20 criteria for a
            good road pricing system and presents case studies
            illustrating the costs, revenues, and benefits of
            alternative congestion charging mechanisms.  The author
            finds that manual tollbooths are not suitable for congestion
            charging because they are land-, labor-, and time-intensive.
            Cordon pricing (as in the Bergen toll ring) can be an
            effective instrument for charging for congestion if half the
            toll lanes are reserved for seasonal pass holders traveling
            through the pricing points at regular highway speed.
            Enforcement of those driving in reserved lanes can be
            carried out by periodic videographs of vehicle license
            plates.  Area licensing schemes require that vehicles
            entering the central business district during peak hours
            prominently display a monthly or daily license.  Enforcement
            is undertaken at gantry points by traffic wardens who
            perform visual checks on the nonstop traffic.  The
            enforcement costs of area licensing schemes are prohibitive
            at motorway speeds but relatively low-cost in a standard
            congested urban setting with limited gateways.  Area
            licensing schemes, also known as supplementary licensing,
            carry the lowest cost per transaction.  Electronic road
            pricing with automatic vehicle identification (an
            off-vehicle recording system) is electronic toll collection
            by time of day writ large and made obligatory on vehicle
            owners in a jurisdiction.  The cost of the electronic
            equipment is not trivial, but is outweighed by the benefits.
            Sensitivity analysis performed on the Hong Kong electronic
            road pricing scheme in 1983-85 shows that even after
            excluding time savings, the savings in operating costs
            produce benefit figures that are greater than system costs.
            The invasion-of-privacy issues that led to the political
            failure of the Hong Kong electronic road pricing scheme can
            not be overcome by giving road users access to confidential
            numbered account arrangements with a prepaid cash deposit.
            The capital cost of electronic road pricing with smart card
            technology (an on-vehicle charging system) is higher than
            the cost for automatic vehicle identification technology
            alone, but benefits still outweigh costs (as in the Dutch
            proposal).  Together, the benefit-cost ratio and the cost
            per transaction are acceptable but this technology is still
            not widely used commercially.  The author argues that
            electronic approaches to direct road use charging are
            superior to manual approaches for road users, road
            authorities, and society as a whole.  And rapid progress in
            microelectronics, cryptology, and microwave technologies
            will continue to yield large-scale economies in the
            manufacturing of automatic vehicle identification equipment,
            read-write transponders, smart cards, and the hardware and
            software that go with them. The author ranks electronic road
            pricing with automatic vehicle identification alone higher
            than electronic road pricing with smart card-type AVI based
            on an unweighted index of all criteria.  And generally, the
            area licensing scheme is superior to cordon pricing.  If
            budgets allow, authorities should investigate the
            feasibility of electronic road pricing.  If the budget is
            tight, they should look into the area licensing scheme with
            its low cost and high benefit-cost ratio (the latter being
            the most important of the 20 criteria the author uses).
            Both conceptually and practically, the author finds that it
            is important to earmark the proceeds of road pricing to
            implement marginal cost pricing in the road sector.