World's Premiere Roadway Detector Evaluation Facility Now "Open for Business"

To meet the need for data of known quality, and to evaluate the increasing number of available roadway detector technologies, engineers from Caltrans' Division of Research & Innovation, working with PATH researchers at UC Irvine (UCI) have developed and deployed a detector evaluation facility that can quickly and automatically determine the operational accuracy of traffic detectors with unprecedented statistical accuracy.

The Traffic Detector and Surveillance Sub-Testbed (TDS2) consists of two contiguous sites on the seven-lane Interstate 405, south of Irvine. TDS2 overhead cameras automatically take a picture of every passing vehicle at both the upstream and downstream sites and re-identify it between the two. This not only provides an absolute ground truth to which other detectors can be compared, but also allows the same detector to be set up at each site to evaluate reproducibility as a function of speed, lane, headway, vehicle type, lighting, or other types of environmental or traffic conditions which may effect detection accuracy. This capability not only determines which detector works best overall, but also determines the specific conditions that cause a particular type of detector to misread. The overall purpose of the TDS2 is to provide a real-world laboratory for the development and evaluation of emerging traffic detection and surveillance technologies relative to: appropriateness for ITS operations and performance measurement, data quality and consistency, ease of use, ease of installation, and overall cost. The growing popularity of the Caltrans PeMS (Performance Measurement System), traveler information, and other ITS functions have placed an increased emphasis on data validity and the detection systems upon which this "intelligence" is based.

The TDS2 has been specifically optimized to assess the accuracy of all types of non-intrusive overhead and side-fire roadway detectors, and compare them with conventional form factor rectangular loops. Although the facility can evaluate any type of detector, it is optimized to evaluate the types of high fidelity detection systems needed for ITS.

Travel time is becoming a very useful parameter for PeMS, ATMIS, incident detection, congestion routing and other functions, and the true travel time estimation requires vehicle characteristics to be re-identified between detection sites. Likewise, Origin/Destination (O/D) data is an essential input for traffic models to make future predictions, and this site can directly assess the applicability of detectors for these types of functions.

The TDS2 has a number of unique capabilities optimized for detector evaluation, which in aggregate, are not duplicated anywhere else in the nation. These high-tech capabilities include:

• The video "ground truth" system, which takes a picture of each vehicle and automatically re-identifies it downstream independent of its lane or speed. • Inductive Signature loops that output the unique waveform or "signature" of each vehicle and then use this information to re-identify each vehicle downstream. This provides independent automatic confirmation of the video re-ID system above. These loop detectors can also output the more conventional bivalent data compatible with 170 and 2070 controllers only with much greater accuracy than is produced by loops at other freeway sites. • Three streaming PTZ video cameras that can be accessed and controlled through any web browser connected to the internet. This is the "CCTV" camera system of the future. • Wireless broadband communication allows all types of information to be available real time across the internet.

The data passes through the City of Irvine, UCI, and Caltrans communication hardware on its way to the Web, in a remarkable institutional synergy of interagency cooperation. Additionally, the TDS2 has two overcrossings with overhead mounting and wiring systems, which can allow detectors to be installed over traffic lanes without shutting down lanes. This in itself is a unique capability not available anywhere else in California. Moreover, the TDS2 is equipped with poles pre-wired for installation of side-fire detectors on the outside shoulder of both sites. One site has also a pole and wiring on the inside shoulder to evaluate HOV detectors and/or dual side-fire detectors.

Finally, the facility includes a completely instrumented freeway offramp. This offramp, in conjunction with a freeway interchange just upstream of the facility, assure a high degree of traffic weaving which has traditionally been very difficult for detectors to detect, but very important for traffic engineers to understand. The TDS2 is on its way to becoming the premier detector evaluation site in the nation. It will help engineers meet the data needs of ITS well into the future.