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16 Source: Jacobs Engineering Group, 2010 Figure 6. Hybrid system. and diagonally dashed bars represent mainline fixed-rate cles is also typically offered. Access requirements and pricing barriers applicable only to cash customers. Since there is only structures for express/HOT lanes vary. In some cases, only one mainline plaza between C and F, cash-paying travelers single occupant vehicles (SOVs) are required to pay a toll, originating at interchange B destined for either C or E pay the while in other cases, SOVs are not permitted access at all, same toll despite the differences in distances traveled. HOV-2 drivers (those with only two occupants) pay a toll or monthly fee, and HOV-3+ drivers (those with three or more occupants) travel toll-free. Some HOT lanes have charged con- Comparison of Toll-Collection Systems stant rates, but increasingly, HOT lanes use some form of value For users of toll facilities, open or hybrid toll-collection sys- pricing (sometimes also called congestion or variable pricing), tems have the advantage of faster traffic movements, improved which adjusts tolls based on traffic periods or conditions. Tolls travel times, and improved safety conditions. However, the are highest during peak travel periods and lowest in off-peak development of open road or hybrid systems requires the periods, with the rates designed to maintain free-flowing traf- installation of an ITS system and the establishment of a cus- fic conditions. tomer service center, which represents an ongoing cost for the To manage congestion, toll agencies have implemented vari- toll-road agency. Open toll-road systems also require ongoing able pricing, in which the toll rate charged depends on the time operational costs relating to customer account maintenance of day (variable/static) or congestion levels (variable/dynamic). and violation enforcement. Open and hybrid toll-road systems Variable/static pricing is defined as having a set schedule of tend to increase throughput, resulting in increased use and rev- tolls that vary throughout the day, often in hourly increments enue generation. However, there may be an increase in revenue based on recent historical data. Variable/static pricing often losses because violators have greater opportunities to avoid includes peak period pricing, which uses price disincentives to payment. Because video tolling can be used in either an open discourage facility use during peak periods. Facilities that have or hybrid toll-collection system, it has been described as a sep- implemented variable/static pricing include the Tappan Zee arate system. Table 3 compares the payment and enforcement Bridge in New York, I-25 in Colorado, SR-91 in California, methods as well as the advantages and disadvantages between Toronto 407, and two bridges operated by Lee County, Florida. closed, open, and hybrid toll-collection systems. Under variable/dynamic pricing, the toll rate fluctuates based on real-time traffic information. This pricing method requires variable message signs that display the toll rate before 2.2.5 Congestion Management the decision point (e.g., the point where a motorist must Toll-road facilities designed for congestion management decide whether to take the toll route or an alternate route). purposes--express lanes and HOT lanes--have been designed The use of variable/dynamic pricing requires the monitoring specifically to improve traffic flow, especially during peak peri- of vehicle speeds, volumes, and/or traffic density. Toll rates are ods. These facilities are typically located adjacent to non-tolled, set according to a predetermined algorithm. Tolls on existing general-purpose lanes in congested urban highways. Access is facilities can change as often as every 3 to 6 minutes. San gained by drivers only if they pay a toll or meet designated vehi- Diego's I-15 express lanes and Minneapolis's I-394 MnPass cle occupancy requirements. Free access to mass transit vehi- express lanes are examples of facilities that use variable/