Although the survey results come from a relatively limited group of responses from toll highway and bridge operators, observation of other toll facilities indicate consistent support for the most popular practices.
Dedicated Lane Plaza Orientation
Almost 90% of responding toll road operators have ETC dedicated lanes, most with multiple dedicated lanes per direction. Most operators and all bridge operators group dedicated lanes together within the conventional plaza. The dedicated lanes are typically located to the left of the manual lanes. Although not captured by the survey results, ramp plazas are often configured differently because of shorter approach zones, a curved roadway alignments, and proximity to other merges or directional splits. Two agencies in Florida, and the Illinois Tollway, among others, locate some or all ramp plaza dedicated lanes to the right, for operational and service reasons. Plazas located on trumpet interchange ramps may group ETC dedicated in the middle of the plaza to equally service traffic entering the plaza from multiple directions.
Dedicated Lane Separation – Same Direction of Traffic
Toll plazas often use extended raised pavement markers within the queue area to augment signing on the plaza canopy and along the approach, as well as extended solid white pavement markings. While this does not provide physical separation, it does help the driver to quickly identify dedicated lanes, and segregate vehicles that are preparing to a stop from those slowing down as needed to navigate a dedicated lane. Raised pavement markings or delineators and solid white markings are also used in the recovery zone.
Dedicated Lane Separation – Opposing Direction of Traffic
Most survey respondents operate plazas with contiguous opposing directions of traffic, but only six of the thirteen physically separate the directions of traffic with a permanent barrier.
Dedicated Lane Utilization
Of fifteen respondents with multiple dedicated lanes, only two operate lanes restricted to cars. Only one agency had installed dedicated lanes restricted to trucks (not captured by the survey since the dedicated lanes were in the process of being converted to mixed use). The majority of toll road facilities operate dedicated lanes without restriction of vehicles classes. Vehicle type, size or height restrictions may be used at tunnel and bridge toll plazas out of necessity due to structural limitations and safety considerations.
Dedicated Lane Width
The average lane width reported was over 11 feet (3.4m), and 12 feet (3.6m) was the most common response. One bridge responded, with a 14-foot (4.3m) lane width. As expected, newer facilities have wider toll lanes than older plaza facilities.
Dedicated Lane Island Widths
These responses varied between only two feet (0.6m) and 16 feet (4.9m). Six to seven feet (1.8m to 2.1m) was the most common survey response. Island widths for dedicated lanes are often established well before the introduction of ETC into a conventional plaza and subsequent conversion of cash lanes to dedicated lanes.
Island widths can be reduced to gain lane width when toll lanes are converted to dedicated lanes, although this increases construction costs and time. Many agencies have adopted standards for toll plaza design. These standards and design practices reflect operating policies and requirements, such as the spacing of stairwells for tunnel access, height of the toll island, equipment. and toll booth horizontal clearances and restrictions on the use of exposed conduit.
Dedicated Lane Posted Speeds
The reported posted speeds ranged from 5 mph to 45 mph (8 kph to 70 kph) with an average of about 26 mph (42 kph). Typical bridge dedicated lane speeds were lower.
Excessive speed through dedicated lanes presents a challenge that all toll facilities incorporating ETC dedicated lanes must face with varying severity. The 85th percentile operating speeds tend to exceed posted speeds, sometimes by substantial margins. Operators implement a variety of measures to encourage or mandate speed compliance.
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