New technologies on Florida’s Turnpike
Retractable delineators, treadles, and AVC being evaluated
In recent months, several innovative technological devices have been evaluated by CUTR for their potential application on Florida’s Turnpike, including retractable highway lane delineators, the Traffic 2000 piezo-electric treadle, and automatic vehicle classification devices. These devices could prove to be valuable to Florida and the Turnpike for increasing safety, assessing tolls more accurately, and auditing toll revenue collected.
Retractable Highway Lane Delineators
The use of orange cones to delineate highway lanes is common practice throughout the U.S. These cones are inexpensive and portable, can withstand impacts from vehicles traveling at high speeds, do not damage vehicles, and are easily recognized. Also, their meaning is easily understood. Currently, they are used to delineate reversible lanes at 32 toll plazas in Florida. This practice works well, but with the addition of electronic toll collection and high speed traffic at these plazas, it will become dangerous for toll plaza attendants to venture into the lanes to move the cones around.
CUTR recently examined an alternative to orange cones—retractable highway lane delineators (RHLDs), which automatically raise up from and lower into the ground by remotely changing the amount of power flowing to the device, thus eliminating the need for workers to go into traffic.
Currently, only one company, TELE-SPOT Systems of Stamford, Connecticut, produces such a device in the U.S., the POP UPTM delineator. In July 1997, several of these devices were installed at an immigration checkpoint on I-15 near San Diego. Other agencies are actively investigating their use: the City of Los Angeles is examining their potential as railroad crossing barriers, and the Port Authority of New York and New Jersey is investigating them for use as reversible lane delineators.
CUTR’s evaluation of the POP UPTM delineator included interviews with agency officials who are working with the device, examination of lab test results on the device, and discussions with TELE-SPOT personnel on an ongoing basis. In addition, three of the devices were loaned to CUTR.
Results of informal lab testing by other agencies indicates that the POP UPTM delineator:
However, lab testing did not accurately predict how these devices would perform in a real-world environment. At the I-15 installation, the POP UPTMs are experiencing a number of problems. Two of the most significant are that they are not simply bending over and popping back up when they are struck by a vehicle, but rather are shearing off the base and flying through the air. Second, they are not waterproof and, therefore, are corroding. These two problems will likely cause them to be replaced with traditional delineation devices in the near future.
- should be able to handle harsh road environments and will not become clogged with sand or grit easily,
- can withstand impacts from vehicles traveling up to 55 mph and will not damage the vehicles, and
- is easily visible and can be equipped with an internal light.
Partially based on CUTR’s recommendation, the Florida DOT’s Office of Toll Operations (OTO) has chosen to wait to purchase any of these devices, to allow them to learn from the installation on I-15 in California. It also allows CUTR time to investigate the true need for reversible lanes through the use of computer simulation modeling. Since electronic toll collection (ETC) will greatly improve the throughput of the toll plazas, there may not be a need for reversible lanes at any of the toll plazas.
Traffic 2000 Piezo-Electric Treadles
To correctly assess tolls and audit the amount of toll revenue collected, Florida’s Turnpike currently uses pressure-sensitive axle detectors, or treadles, produced by The Revenue Market, Inc. (TRMI) to detect vehicle axles in their toll plaza lanes. These treadles consist of two, three, or four parallel metal strips held apart by regularly-placed spacers. As wheels of the vehicles pass over the treadles, the strips act as electrical switches and generate a signal by which each axle is detected. The devices must be extremely accurate and work in a range of adverse conditions.
As part of the Turnpike’s SunPass program, a different type of treadle, the Traffic 2000 piezo-electric treadle, is being considered for installation on the Turnpike’s ETC-dedicated and express lanes (high speed lanes). Testing indicates that these treadles are suitable for counting axles in high speed (greater than 5 mph) applications—for example, for traffic counting on an interstate highway. However, piezo-electric treadles have traditionally been unable to accurately detect axles in low speed (less than 5 mph) conditions such as those at conventional toll plazas.
To address this problem, Traffic 2000 recently developed a new piece of sofware. However, determining the true effectiveness of these treadles with the new software is difficult because all results to date are based on a two-day test on the Dallas North Tollway. While the device performed exceptionally well during this limited test, there are several adverse conditions in which this treadle has not been tested, particularly with slow-moving traffic.
With only two similar systems operating in the United States, forecasting the possible maintenance requirements and operational benefits is difficult. However, the design of the device is such that it should last longer than the treadles used now, it will be easier and cheaper to replace, the initial costs are significantly lower, and the installation easier than with the current treadles.
Due to the limited evidence available on the accuracy of piezo-electric treadles at low speeds, further testing is essential to determine their accuracy, durability, and reliability in the low speed ranges. It was recommended that sample treadles be obtained from Traffic 2000 for independent testing and evaluation. They should be tested comprehensively to work under different conditions such as in slow-moving and fast-moving traffic, adverse weather conditions, situations involving human interference with the devices, and instances of vehicles traveling at an angle over the treadles. As a result of this recommendation, the OTO has begun testing of the Traffic 2000 treadle at one of its South Florida toll plazas.
Automatic Vehicle Classification (AVC) Technologies
Automatic vehicle classification systems apply advanced technologies to improve vehicle classification for toll collection systems. Vehicles can be classified by number of axles, dimensions (height, length, wheel base, height over first axle), weight, number of occupants in the vehicle, or purpose for which a vehicle is being used (for example, a special class is assigned to taxi cabs). Toll agencies use these classifications to determine the correct toll for each vehicle.
Florida DOT uses an overhead-mounted ultrasonic device and a treadle to automatically classify vehicles by their number of axles. The ultrasonic device separates vehicles while the treadle lies flush with the pavement and counts vehicle axles; this combination reveals the number of axles in each vehicle. The existing overhead ultrasonic device has a transducer that acts as the transmitter and receiver of ultrasonic waves and electronic equipment for analyzing these waves. The active part of the transducer is a membrane that vibrates to produce the waves. Quite often, this membrane does not function as expected, and the ultrasonic device has become a sufficient maintenance problem as to be "unacceptable" to the OTO.
CUTR investigated capabilities of various new vehicle separation technologies, primarily those based on pulse laser, ultrasonic, and active infrared. At least nine of the larger ETC agencies around the country are using light curtains, which scan a vertical plain for presence of objects, in their AVC systems. In combination with triggering loops and treadles, light curtains currently appear to provide one of the most efficient techniques for automatic vehicle classification. However, a newly-improved version of the overhead ultrasonic device and a newly-developed algorithm for inductive loops (Idris) both appear promising. Other vehicle separator technologies are available, but none seem capable of offering the reliability needed by Florida DOT.
With Peek Traffic, Inc., and OTO, Idris and the improved transducer for ultrasonic overhead were tested in the Anderson Mainline Toll Plaza at Veteran’s Expressway in Tampa. For the three-day, six-hour comparison, Idris recorded a 99.76% accuracy rate, and the improved overhead ultrasonic device recorded an accuracy rate of 99.34%. The number of vehicles passing through the lane during the six-hour peak periods was 1,661.
The second phase of this testing will include vehicle separation field tests under various traffic and environmental conditions and examination of Idris for other ETC applications (such as a triggering mechanism for ETC violation and license plate image capture).
All these devices could prove beneficial to Florida’s Turnpike, and further evaluations will be conducted. "CUTR has provided--and continues to provide--the Office of Toll Operations with a valuable service," said Jim Davis, Florida DOT Deputy Director for Facilities and Equipment in the OTO. "Their investigations and subsequent recommendations on equipment are an essential part of our decisionmaking process."
For further information, contact CUTR ITS Program Director Mike Pietrzyk, (813) 974-9815, or Research Associate Mark Burris, (813) 974-9809.
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