The most significant limitation of the DITSEM model is that it is currently capable of CO emission estimation only. This is perhaps the main reason why this model has not been adopted as a tool in practice. Nevertheless, Washington and others have applied many theoretical aspects of the model in more recent work at the Georgia Institute of Technology .The impact of these results is expected to be significant for the determination of the emission benefits of ITS technologies. Early results show that the surface for HC emission rates may actually be quite flat for all values of speed and acceleration, except for a slight hill in the region where both speed and acceleration rate are high. If this proves to be true, the implications for the assessment of emissions from transportation plans will be substantial. It suggests that there is little to no benefit to be gained through flow smoothing, with respect to HC emissions. On the positive side, however, this also shows that there is not likely to be a significant increase in HC emissions as a result of higher travel speeds. Even for high acceleration rates , the potential increase in HC emissions at high speeds appears to be less than 30 percent. This would lead to quite different conclusions than the previous evidence that moving from moderate travel speeds to very high free flow speeds is likely to significantly increase HC emission rates . The modal emission model being developed by researchers at the UC Riverside and the U of Michigan is a comprehensive modal emission model for light-duty cars and trucks. It is based on a parameterized physical approach and consists of six modules that predict: 1) engine power; 2) engine speed; 3) air/fuel ratio; 4) fuel use; 5) engine-out emissions; and 6) catalyst pass fraction. The model also accounts for four vehicle operating conditions: 1)cold and warm starts; 2) normal, stoichiometric operation; 3) high-power enrichment; and 4) lean-burn operation.

UC Riverside researchers have recruited and tested 327 vehicles , collecting second-by-second tailpipe and engine out emissions. These data have been combined with on-road emission data to formulate and calibrate the emission model. The model has been formulated for different vehicle/technology groups and addresses malfunctioning/high-emitting vehicles.With respect to these four ITS technologies,dutch buckets for sale previous research indicates that they generally reduce emissions, although caveats apply to each technology and/or its application or both. Table 1 presents a “snapshot” of select findings from previous studies on the environmental impacts of these technologies and applications. The technologies in Table 1 are arranged into three groups. The first group are “supply side” enhancements such as advanced traffic signal coordination and in-vehicle route guidance. The technologies in this group reduce emissions and fuel consumption by increasing highway capacity and, in turn, lead to smoother traffic flow and reductions in congestion-related emissions. The second group of technologies are “demand/emissions management” such as pre-trip ATIS and congestion pricing . These technologies can reduce emissions and fuel consumption by either reducing the amount of travel or encouraging other changes in travel behavior . Estimates of fuel consumption reductions due to ATSC and in-vehicle information and navigation systems range from 3.0 to 13.1 percent; estimated reductions in CO emissions range from 5.0 to 13.6 percent; and estimated reductions in HC emissions range from 4.0 to 13.0 percent. Of the emission results summarized in Table 1, only NOx estimates possible increases. Three studies show different results: an increase of 4.2 percent, essentially no change, or a decrease of 13.0 percent in NOx emissions. This last result highlights the appropriate interpretation of the ranges of impacts shown in Table 1. That is, these results reflect differences in ITS technologies, implementations, and study methodologies—they are not estimates of the range of real world benefits.This section builds upon the previous “snapshot” overview by providing a more detailed review of some of the literature that has attempted to provide quantitative assessments of the impacts of ITS technologies and user services. It is not intended to be an exhaustive review, but rather it is intended to provide sufficient level of detail for the more extensive efforts to follow.

To the extent possible, results in this section are separated into assessments based on the results of field operational tests and those based on modeling studies. However, it should be noted that there is some overlap, due to the fact that some modeling studies have attempted to simulate real-world ITS deployments. Furthermore, many of the conclusions from FOTs have been drawn from the results of modeling studies that have applied data collected during the FOT to simulate the impacts at another level. For example, Van Aerde and Rakha applied some measures of traffic impacts to simulate environmental impacts.A large number of FOTs have been conducted, are currently underway, or are being planned across the U.S. Unfortunately, the focus of most of these tests has been primarily to determine the operational performance and reliability of the ITS technologies themselves, not to evaluate either their traffic or environmental impacts. Some information has been obtained regarding the effects of various technologies on traffic operations and driver behavior, but little effort has been made to directly assess the environmental impact of ITS deployment. This is due in part to the difficulty of actually measuring energy and environmental benefits. The only reasonable assessment of the environmental benefits directly from FOT is a highly localized emission measurement at a specific system site, such as an intersection or a ramp meter. In this section, we summarize here the results of two comprehensive reviews of ITS FOTs. The first of these is the most comprehensive collection of results from FOTs that review the impacts of ITS deployment. This review was performed at Mitretek, and the results are contained in a series of reports from US DOT . The most recent of these US DOT reviews provides qualitative and quantitative evaluations from FOTs and modeling studies. We also summarize a review prepared by Little and Wooster’s . US DOT discusses the benefits of the application of ITS in the context of the goals of the National ITS Program plan. The goal that is directly relevant to this project is: “Reduce energy and environmental costs associated with traffic congestion.” This goal has three primary objectives: “reduce harmful emissions per unit of travel, reduce energy consumption per unit of travel, and reduce new transportation right-of-way requirements.”In addition, Shank claims that traveler information can have a small positive effect on emissions, citing results from the Boston SmarTraveler ATIS program . The interesting thing to note here is that although the emission reductions were estimated to be significant for participating travelers,hydroponic net pots only a small proportion of the total number of trips in the metropolitan area were expected to be affected.

Hence, the system wide benefits are small. Little and Wooster discuss the fundamental elements and relationships that must be considered by FOTs in order to evaluate the emission and fuel consumption impacts of ITS technologies and user services. FOTs with environmental evaluation objectives in the United States, Europe, Japan, and Australia are identified and findings on the environmental impacts of ITS for completed FOTs are discussed. The paper also discusses the State-of-the-practice for environmental evaluation of ITS technologies in field settings, including experimental design, data collection, and analytical methods. The ATMS-related tests identified in the U.S. include ATSAC , FAST-TRAC, and SMART Corridor , which all demonstrate the impacts of dynamic signal coordination on arterial traffic flow. The SMART Corridor project also includes testing of dynamic ramp metering. Little and Wooster briefly describe a range of other tests involving the deployment of ATIS, Emergency Management Systems , APTS, and CVO technologies and user services. They conclude that the FOTs with published results indicate favorable environmental impacts for ITS technologies and user services. However, they note that most of these tests address more conventional traffic management user services, such as dynamic signal coordination, and tests of ATIS and APTS user services are not well represented. Little and Wooster reported that the focus of most of the FOTs had been on “technical feasibility and, to a lesser extent, user response.” They found that in the U.S. a number of the FOTs were struggling to identify appropriate data collection and analytical techniques to determine environmental impacts. The need and importance of a standard evaluation framework was highlighted to allow proper comparison of ITS technologies. Similarly, large emission reductions can be achieved at individual ETC facilities; however, the overall benefit is dependent on the frequency of toll plazas. A report by the Clean Air Action Corporation. estimated the average emission reductions to be 72 percent for CO, 83 percent for HC, and 45 percent for NOx, per mile of impacted operation. However, these results are based on the assumption that the distance involved in the average barrier toll transaction is only 0.55 miles. Hence, the reductions, although large, are highly localized and may be insignificant at the network level. The Clean Air Action Corporation estimates are based on a study of the MuskogeeTurnpike in Oklahoma, Asbury Plaza on the Garden State Parkway in New Jersey, and the Western Plaza on the Massachusetts Turnpike. Adaptive traffic signal coordination has significant potential for providing energy and environmental benefits. The ATSAC program in Los Angeles California reported a 13 percent reduction in fuel consumption and a 14 percent reduction in vehicle emissions. Similarly, the City of Abilene ATSC system estimated a 6 percent reduction in fuel consumption, 10 percent reduction in HC emissions, and a 13 percent reduction in CO emissions. In contrast, NOx emissions were estimated to increase by 4 percent.Results from FOTs can be useful for studying the potential benefits of ITS deployment. However, it is difficult to make robust comparisons of ITS systems from the performance of FOTs since each environment is different and most test conditions cannot be varied systematically. Hence, the majority of environmental evaluations of FOTs are the result of qualitative assessments, or are made by computer modeling using measures of travel behavior and traffic performance obtained from the FOT. Simulation models can be very useful tools to study the benefits of various ITS technologies and the benefits of differing configurations of individual technologies.With a modeling tool designed to simulate aspects of ITS technologies, controlled studies can be conducted with different traffic demand patterns, different levels of market penetration, and different optimization strategies. Such simulations can provide information to facilitate the identification of ITS deployment levels and specific strategies that are most likely to have positive measurable impacts on the transportation system. This section provides a review of several modeling studies that have provided some quantitative assessments of various real-world and modeled deployments of ITS technologies and user services under differing scenarios. It should be noted that all the modeling studies discussed here that applied INTEGRATION used earlier versions of the model than are available now, and some of the limitations of these versions of the model do not exist in the latest version.The general conclusion drawn from the results of these simulations was that the application of the ATMS user services provided a general increase in speed and a reduction in total delay. Maximum benefits were achieved with the simultaneous implementation of signal coordination on arterial streets and ramp metering on freeway facilities. However, despite the increased speeds and reduction in total delay, the impact on various measures of effectiveness on the parallel arterial varied widely for each scenario tested. The nature of the signal coordination had a marked effect on the parallel arterial performance. However, the freeway data indicated that most of the scenarios tested influence freeway operation in a consistent manner. The only exception was Scenario 2 , which produced very different results due to the absence of any form of ramp metering. The benefits of ramp metering were found to be significant reductions in delay without encountering increases in congestion. Average speeds increased and emissions of CO and HC both decreased. However, fuel use and NOx emissions increased, as did the number of accidents and injuries.A warning was issued that “future simulation projects should be very conservative in their estimation of the effort required for data collection and coding, model testing and calibration, and investigations.