Performance measures are needed to inform decisions regarding the overall level of resources to devote to transportation, where to allocate these resources, and how best to use them. The first two types of decision require regular monitoring of the system to reveal problems, which present opportunities for improvement. A few, easily measured indicators of the major benefits and costs of the system are appropriate for this task. For the third type of decision, how to best address a specific problem, a more comprehensive set of benefits and costs must be considered. Indicators must be found for those benefits and costs that would be impacted by alternative means of addressing the problem, so that the overall impacts of the alternatives can be compared. This report discusses the benefits and costs of transportation and recommends specific measures to use as indicators of the benefits and costs, as well as data sources and methods of measurement. It discusses the role of intelligent transportation systems as both an object of measurement and a means of measurement

Motivated by the need for better utilization of existing high-occupancy vehicle (HOV) lanes and the potential of high-occupancy/toll (HOT) lanes to increase utilization, this paper examines the circumstances in which HOT lanes could provide a more desirable alternative to HOV lanes. First, it compares the HOT and HOV lane concepts, showing how they are similar and how they differ. Both involve finding some type of equilibrium in which no additional people are motivated to use the lane. However, in the case of the HOT lane, the agency operating the facility can affect the equilibrium point by varying the toll, thus having the potential to increase lane utilization and reduce overall delay. HOT lanes also offer travelers the additional choice of a delay-free trip if they choose to pay a toll. The question of how sensitive users are to the toll level was investigated using data from SR 91, in Orange County. During the first two years there was no toll for HOVs, so the toll lanes operated as true HOT lanes, even though they were officially named Variable Toll Express Lanes. Eastbound toll lane traffic showed a very low elasticity with respect to tolls-between -.02 and -.16. This means that if tolls are reduced by 50%, toll lane volumes will increase by between 1% to 8%. The westbound analysis found a positive relationship between tolls and toll lane traffic. This unreasonable result appears to be the result of a positive correlation between tolls freeway traffic volume that makes it impossible to separate the effects of the two variables. But this result also suggests that in the westbound direction toll lane volumes are not very sensitive to tolls. The final section of the paper uses a model to compare the performance of an HOV, HOT, and mixed flow lane in various circumstances. In all cases modeled, a HOT lane results in substantially less delay than an HOV lane. It also performs better or almost as well as a mixed flow lane. HOV lanes perform better than mixed flow lanes under extreme congestion and when there is a fairly high proportion of HOVs before the HOV lane is established. These conditions result in good utilization of the lane and provide the motivation for travelers to shift to HOVs. Under less extreme congestion, and when the initial proportion of HOVs is low, mixed flow lanes perform better than HOV lanes. These findings suggest that in locations where tolling would be feasible and where HOV lane utilization is low, HOTs might be a preferable alternative to the HOV lane. However, before conversion of a particular lane there should be more detailed modeling to confirm that an HOT lane would perform as expected and to determine the effects of the conversion on the network in which the HOV lane is located.

Acceptance of ITS components that are designed to increase capacity will hinge on the extent to which additional capacity induces additional travel. This study addressed methodologies for studying the effects of capacity on travel: 1) before and after studies or travel times and volumes in corridors in which capacity had been increased, 2) surveys of users of routes on which capacity had been increased, and 3) statistical changes in county VMT as a function of freeway capacity. On I-80 in the Bay Area, the site selected for the investigation, travel times and volumes were quite variable. This suggests that a fairly high volume of data are required to draw conclusions about changes in volumes. Furthermore, construction destroyed most of the existing loop detectors, and new detectors were not connected immediately. Thus such comparisons may not be possible in the short term if researchers do not have an alternate method of obtaining a sufficient quantity of volume data. A survey was designed, but was not tested, because it was decided to survey travelers on I-80 rather than Route 85 as initially planned in order to use the survey to explain whatever differences were observed and to provide information on the extent to which the travel time savings motivated changes in job or housing location. The statistical analysis of changes in VMT based on Smog Check data did not prove feasible because the data were not available at a level of aggregation needed for such an analysis. Key word: effects of capacity increases, induced demand, latent demand

The success of a high occupancy vehicle lane in motivating people to shift to carpools and buses depends on maintaining a travel time differential between it and the adjacent general purpose lanes. This differential, in turn, depends on the level of continuing delay on the general purpose lanes. Therefore, it is clear that a high occupancy vehicle lane that will motivate people to shift to high occupancy vehicles will not eliminate congestion. Consequently, it is not clear that constructing a high occupancy vehicle lane will necessarily reduce delay more than construction of a general purpose lane. The objective of this research is to determine the circumstances in which this would be the case. The hypothesis is that such circumstances would be quite limited, and this proves to be the case. The intended benefits of high occupancy lanes are defined as reduced person-delay and reduced emissions. A model is developed to calculate these benefits for four alternatives add a high occupancy vehicle lane, add a general purpose lane, convert an existing lane to a high occupancy vehicle lane, and do nothing. The model takes into account the initial conditions, the dynamic nature of the travel time differential between the high occupancy vehicle lane and other lanes, and the uncertainty regarding the extent to which people will shift modes. It combines queueing theory and mode choice theory and provides a robust method for comparing alternatives using a small amount of easily observed data. Application of the model in typical situations shows that with initial delays on the order of 15 min or more, adding a high occupancy vehicle lane would provide substantial reductions in delay and some reduction in emissions. However, in a wide range of such situations, adding a general purpose lane would be even more effective. Only if the initial delay is long and the initial proportion of high occupancy vehicles falls in a rather narrow range, would an added high occupancy vehicle lane be more effective. The proportion of high occupancy vehicles must be such that it allows good utilization of the high occupancy vehicle lane while maintaining a sufficient travel time differential to motivate a shift to buses or carpools. Adding a high occupancy vehicle lane to a three lane freeway will be more effective than adding a general purpose lane only if the initial maximum delay is on the order of 35 min or more and the proportion of high occupancy vehicles is on the order of 20%. Federal policies encourage construction of high occupancy vehicle lanes and restrict funding for general purpose lanes in areas that have not attained air quality standards. The findings of this research suggest a need to reconsider these policies.

It is well known among HOV practitioners that the success of a high occupancy vehicle (HOV) lane in motivating people to shift to HOVs depends on maintaining a travel time differential between it and the adjacent general purpose lanes. This differential exists only if there is continuing delay on the general purpose lanes. The paradox inherent in this requirement – that HOV lanes as a congestion reduction measure require the continuance of congestion – is rarely noted. Because of this requirement for continuing congestion, it is not clear that construction of an HOV lane will always reduce delay or vehicle emissions more than construction of a general purpose lane. The objective of this research was to determine the circumstances in which this would be the case. The hypothesis was that such circumstances would be quite limited, and this proved to be the case.

A model was developed to calculate person-delay and emissions for four alternatives: add an HOV lane, add a general purpose lane, convert an existing lane to an HOV lane, and do nothing. The model required relatively few inputs: the beginning and ending time of the congested period, the time of the maximum delay, the length of the maximum delay, the number of lanes and the capacity per lane, the proportion of HOVs, and the average occupancy of HOVs and non-HOVs (hereafter referred to as LOV3 for low occupant vehicles). Application of the model in typical situations showed that if the initial proportion of HOVs is .15 or greater, adding an HOV lane would eliminate or substantially reduce delay. However, in a wide range of such situations, adding a general purpose lane would be even more effective. Only if the initial delay is long and the proportion of HOVs falls in a rather narrow range would an added HOV lane be more effective. In these cases the proportion of HOVs must be such that it allows good utilization of the HOV lane while maintaining a sufficient travel time differential to motivate a shift to HOVs.

High occupancy vehicle (HOV) lanes are being promoted as a way to reduce congestion and air pollution on urban freeways. While constructing new general purpose lanes is often seen as environmentally destructive, constructing new HOV lanes is seen as good for the environment and effective in reducing congestion. The reality, however, is that although both are effective in reducing emissions and congestion, construction of a general purpose lane will be more effective in a wide range of typical conditions.

The City of Los Angeles and Caltrans would like a simulation testbed for testing alternate traffic management strategies in the Santa Monica corridor. This study assesses the data available for such a simulation and describes data needs, potential sources, and data preparation required. It presents a work plan and resource requirements for acquiring the necessary data. The Appendix analyzes the conditions under which a simulation testbed is worthwhile. This study supported another PATH project, Los Angeles Smart Corridor Simulation Feasibility Study (MOU 270), which analyzed candidate models for the simulation and determined their data requirements. Key words: Data, transportation modeling, traffic simulation, Santa Monica Corridor, Smart Corridor

A method for determining how to develop the most effective traffic surveillance investment program given available resources is developed. The complicated decision structure for deciding where and when to install traffic surveillance and what type of surveillance to install is broken down into a series of steps: identifying information needs, determining which can be met by traffic surveillance, setting criteria for and evaluating the benefits of surveillance in various locations, identifying alternative surveillance methods and estimating their capabilities and costs, comparing the ratios of benefits to costs, and finally matching cost-effective investments with available funds.