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Table 3. Comparison of closed, open, and hybrid toll-collection systems.
Toll System Closed Toll
Open Toll Collection Hybrid
Option Collection
Description Drivers pay at Gantry-mounted Mixture of barriers, ETC,
and payment manned tollbooths collection equipment and/or video tolling
method or at automated ETC-only lanes
coin machines
Gates possible but not
(ACMs)
likely
Lanes have gates
Enforcement Gates Video cameras Some gates
method Video cameras Police Video cameras
Toll attendants Bills are mailed Toll attendants
Police Bills are mailed
Police
Advantages Fewer violations if Increased throughput Balances increased
gated along the facility throughput and traffic
Lower probability Increased revenues flow with lost revenues
of customer Minimum violation rate
account errors at gated areas
Strategically placed
gates
Disadvantages Gates decrease Account management Incurs both barrier
throughput and back office costs system and ETC costs
Cost for tollbooths Violation processing Bottlenecks/accidents at
and attendants and collection costs, collection points due to
Bottlenecks at (e.g., court, collection driver confusion
tollbooths agencies, liens) Higher violation rate
Employee theft High violation rate than gated system
without gates leading
Equipment
to more lost revenues
malfunctions
Legal actions can
Increased potential
result in negative
for accidents at
publicity
tollbooths
Lower throughput
can result in lower
revenue
generation
Source: Jacobs Engineering Group, 2010
dynamic pricing. Figure 7 summarizes the existing and planned · Variance: An error in the toll communication system that
projects in the United States that involve the development of occurs when something between the onboard and roadside
HOT lanes, express lanes, or variable pricing mechanisms. dialogue has failed.
· Violation: A record of an unpaid toll that occurs when a cus-
tomer does not pay the proper amount.
2.2.6 Leakage Rates
· Transaction: A time-framed event occurring in the toll lane
The calculation of leakage rates is a common practice used representing either a cash or electronic toll. The transaction is
by toll agencies to estimate the number of transactions for identified by all or a combination of the following parameters:
which they have not received payment. Below are the defini- location, time, date, vehicle class, vehicle ID, and toll amount.
tions used by the International Bridge, Tunnel and Turnpike
Association (IBTTA) with regard to toll violations and leakage: Because of the different disclosure requirements, system
configurations, technologies employed, and metrics used, it is
· Leakage: Transactions where no revenue has been collected relatively difficult to provide a direct comparison of toll agen-
or revenue is not fully collected. Leakage does not include cies with respect to toll leakage. While some agencies will dis-
non-revenue or violation transactions wherein the vehicle is close debt that has been written off and/or disclose the amount
either not permitted to cross the barrier or where a violation of revenues that may not be collected, the manner in which
image is taken. these numbers are derived and the factors that influence these
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Source: AE COM, 2006
Figure 7. Congestion management projects in the United States.
parameters are not always apparent. It should be noted that barriers throughout the system (e.g., gates, retaining walls,
industry rules of thumb estimate toll system leakage to be and/or Jersey barriers) will likely have lower leakage rates.
between 5% and 10%. Below are some of the main issues that Along these same lines, it is more difficult to directly make
influence the reporting of toll leakage: the following comparisons: (i) systems with single-project
authorities versus multi-project toll systems, (ii) urban ver-
· Limited information disclosure: Because of the sensitivities sus rural systems, and (iii) toll systems with mostly long-
involved, some toll-road authorities may be reluctant to distance roads versus bridge systems.
publicly report leakage information, especially if leakage · Technology used for enforcement: The estimation of leak-
rates are relatively high. The publication of leakage informa- age rates will also be affected by the extent to which the sys-
tion could have negative impact on existing debt obligations tem uses cash rather than electronic toll collection. A mostly
as well as potentially encouraging additional violations. Sim- cash system will place greater reliance on more physical
ilarly, private-sector developers that are publicly traded tend measurements of road usage such as gates, in-lane traffic
to avoid the publication of this information since this could count equipment, eyewitness reports, and traffic citations.
have a negative impact on their stock price. In contrast, ETC systems will rely more heavily on camera
· System configuration: System configuration will also affect and video recognition systems. Similarly, leakage rates may
toll-system leakage rates. Toll systems with more access and differ on systems that collect front and back license plate
entry points will likely have higher leakage relative to compa- information versus ETC systems that use only back license
rable toll systems with fewer entry points. Similarly, toll sys- plate information. The inability to trace temporary or other
tems that use and maintain a higher percentage of physical paper license plates will also affect toll-system leakage rates.
