【正文】 flow data, as well as the ease of data interpretation and integration into the existing traffic control system. Current vehicle detection is based predominantly on inductive loop detectors (ILDs) installed in the roadway subsurface. When properly installed and maintained, they can provide realtime data and a historical database against which to pare and evaluate more advanced detector systems. Alternative detector technologies being developed provide direct measurement of a wider variety of traffic parameters, such as density (vehicles per mile per lane), travel time, and vehicle turning movement. These advanced detectors supply more accurate data, parameters that are not directly measured with previous instruments, inputs to areawide surveillance and control of signalized intersections and freeways, and support of motorist information services. Furthermore, many of the advanced detector systems can be installed and maintained without disrupting traffic flow. The less obtrusive buried detectors will continue to find applications in the future, as for example, where aesthetic concerns are dominant or procedures are in place to monitor and repair malfunctioning units on a daily basis. Newer detectors with serial outputs currently require specific software to be written to interpret the traffic flow parameters embedded in the data stream. Since each detector manufacturer generally uses a proprietary serial protocol, each detector with a unique protocol requires corresponding software. This increases the installation cost or the real purchase price of the detector. Furthermore, not every detector outputs data on an individual vehicle basis. While some do, others integrate the data and output the results over periods that range from tens of seconds to minutes, producing parameters that are characteristic of macroscopic traffic flow. The traffic management agency must thus use caution when paring outputs from dissimilar detectors. In performing the technology evaluations and in analyzing the data, focus was placed on the underlying technology upon which the detectors were based [1,2]. It was not the purpose of the program to determine which specific detectors met a set of requirements, but rather whether the sensing technology they used had merit in measuring and reporting traffic data to the accuracy needed for present a nd future applications. Obviously, there can be many implementations of a technology, some of which may be better exploited than others at any time. Thus, a technology may show promise for future applications, but the stateoftheart of current hardware or software may be hampering its present deployment. The detectors that were used in the technology evaluations during the field tests are listed in Table 1. Not all detectors were available at all sites as shown in the footnotes to the table. A summary of the advantages and disadvantages of the detector technologies is given in Table 2. Some of them are application specific, implying that a particular technology may be suitable for some but not all applications. A factor not addressed in this table is detector cost. This issue is again application specific. For example, a higher cost detector may be appropriate for an application requiring specific data or multiple detectio