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Traffic engineering studies such as validating Highway Capacity Manual (HCM) models require complete and reliable field data. However, the wealth of intelligent transportation systems (ITS) data is sometimes rendered useless for these purposes because of missing values in the data. Many imputation techniques have been developed in the past with virtually all of them imputing a single value for a missing datum. While this provides somewhat simple and fast estimates, it does not eliminate the possibility of producing biased results and it also fails to account for the uncertainty brought about by missing data. To overcome these limitations, a multiple imputation scheme is developed which provides multiple estimates for a missing value, simulating multiple draws from a population to estimate the unknown parameter. This paper also develops a framework of imputation which gives a broad perspective so that one can relate imputation methods to each other. DOI: 10.1061/(ASCE)0733-947X(2005)131:12(931) CE Database subject headings: Intelligent transportation systems; Traffic capacity; Data processing.

This paper describes validation results of a video image processing systems: PEEK VideoTrak 900. For this research, 12 PEEK VideoTrak 900s were installed on Interstate Highway I-75 in the Atlanta metropolitan region, and traffic movements were videotaped during several time periods. The test results showed that tracking strip type and location are critical factors in obtaining the best data accuracy. The test results showed that the system provided relatively stable speeds, but some cases showed huge volume errors. The system provided reasonable volume and speed results during the daytime, but its performance diminished during the nighttime. DOI: 10.1061/(ASCE)0733-947X(2003)129:4(462) CE Database subject headings: Imaging techniques; Vehicles; Traffic surveillance; Data collection; Traffic flow; Georgia.

Police radar is known to have an effect on the speed of drivers. This effect derives from the presence of vehicles equipped with radar detectors in the traffic stream and the reactions that the drivers of these vehicles have to radar. The level of impact on a traffic stream exposed to radar transmissions is a function of the proportion of radar detector equipped vehicles in the traffic stream, i.e., the radar detector density. Microscopic simulation can be used to model this impact. A microscopic simulator extension is proposed that allows determinations of this type to be carried out by adding the capability to model driver response to radar transmissions. This approach can also be applied to the modeling of other driver warning technologies such as changeable message signs. A case study using the proposed methodology to analyze different congestion and radar detector density levels is presented and discussed. The case study shows that the efficacy of using radar as a speed reduction strategy is a function of congestion and radar detector density, with the strategy being most effective for volumes levels between 200 and 1,400 vehicles per hour per lane. CE Database keywords: Traffic flow; Radar; Simulation; Speed control.

A signal timing policy describes operational goals applied when developing a timing plan for a system of coordinated intersections. This research investigates differences in signal timing plans resulting from implementation of five basic signal timing policies (including minimizing delay, minimizing stops, minimizing fuel consumption, maximizing coordination bandwidth, and a 'baseline' policy). Further, this research investigates differences arising from application of different techniques to achieve the same policy goal (e.g., different techniques to maximize coordination bandwidth). Volume and other traffic signal data from four traffic signal systems are collected. Various computer tools including PASSER II-90 and TRANSYT-7F are used to develop signal timing plans that emphasize each policy. For the maximum bandwidth policies, several techniques for achieving the policy goal are applied. In all cases, the resulting signal timing plans are transferred to TRANSYT-7F for comparative simulation of detailed systemwide and route-specific measures of effectiveness. Review of these measures of effectiveness provides insights into the relative success of each timing policy, and the impacts of each policy on route-specific and overall system performance. Based on these insights, general guidelines for application of signal timing tools are proposed.

An alternative approach to the estimation of the critical cornering speed of large combination vehicles is presented. Existing techniques are based on analytical models subject to a series of simplifying assumptions, and do not explicitly consider grades and other three-dimensional roadway features of the real problem. One result of this study indicates that these simplified models may overestimate critical cornering speed by as much as 50%. The proposed technique combines detailed simulation of the dynamics of the motion of large combination vehicles through a three-dimensional roadway, with a Monte Carlo sampling of possible vehicle configurations and component mechanical properties to produce databases for statistical analysis. This approach is applied to the study of critical cornering speed at freeway-to-freeway connectors. Databases for several samples of vehicles are generated, and a series of regression models that predict critical cornering speed is created. Results indicate that these regression models may be used to predict critical cornering speed to a high degree of accuracy. Finally, critical cornering speeds estimated using these models compare reasonably with actual speed data collected at five freeway connectors.