Janusz Supernak

Temporal utility profiles of activities and travel: Uncertainty and decision making

This paper further develops the concept of analyzing the temporal utility profiles of actions, i.e. activities accompanied by the associated effort such as travel. This approach integrates elements of different approaches aimed at studying travel behavior, such as activity-based approaches, utility maximization theory and dynamic analysis. It generally intends to broaden the context of studying human travel behavior by focusing primarily on activities as a primary reason for travel. The nature of the competition among alternative chains of actions is discussed within a modified context of utility maximization theory. The issue of constraints in travel-related choices is explored. Introduction of the uncertainty element appears to contribute toward further refinement of the utility profile concept. Extensions of the proposed approach as well as its potential applications are discussed.

SAN DIEGO'S INTERSTATE 15 CONGESTION PRICING PROJECT: ATTITUDINAL, BEHAVIORAL, AND INSTITUTIONAL ISSUES

Attitudinal, behavioral, and institutional findings are summarized from the evaluation of the Interstate 15 (I-15) congestion pricing project, a 3-year demonstration that allowed single-occupant vehicles to use the existing I-15 high-occupancy-vehicle lanes, known as the I-15 express lanes, for a fee. The project was part of the FHWA Congestion Pricing Pilot Program and was managed by the San Diego Association of Governments. San Diego State University conducted an independent, multielement evaluation of the project. FasTrak offered all travelers on I-15 a choice of whether to pay for the use of the lanes. FasTrak users saved time by using the express lanes. The most-cited reason to join FasTrak was the need for on-time arrival. FasTrak users and I-15 carpoolers continuously perceived traffic conditions in the I-15 express lanes as satisfactory. A majority of FasTrak customers and an increasing fraction of I-15 carpoolers considered the project successful. Equity issues did not emerge despite the fact that FasTrak users came from the highestincome groups. Potential business interest in a program like FasTrak primarily hinges on the company’s perceived dependency on a corridor in which the program is installed. Homeowners surveyed considered the I-15 pricing program as a secondary factor in their decision to relocate along the I-15 corridor. Many involved in implementing the project perceived that the project matched or exceeded their expectations. They stated that it proved that pricing was a technically and politically viable strategy. The media satisfactorily informed the public about the project.

A Panel-Based Evaluation of the San Diego I-15 Carpool Lanes Project

The operation of reversible high-occupancy vehicle (HOV) lanes on Interstate 15 north of San Diego, California, has been monitored by an annual panel survey of commuters in the region and by traffic flow observations. The panel survey, initiated in 1988, collected mode choice, travel time, and attitudinal data in one wave prior to the opening of the lanes and in two waves after the opening of the lanes. These data are used to model the causes of changes in four variables at three points in time: (1) choice of ride-sharing versus solo driving, (2) travel time, (3) perceptions of traffic conditions on the I-15 mixed-flow lanes, and (4) attitudes concerning the HOV lanes. The model involves simultaneous equations with mixed discrete-choice, ordinal-scale and continuous variables, estimated by probit sub-models and distribution-free generalized least squares. An important feature is the use of individual-specific constant terms, which take advantage of repeated measurements on the same individuals to account for population heterogeneity. Results show mutual cause and effects among mode choice, travel times, and attitudes.

Dynamic value pricing on I-15 in San Diego: Impact on travel time and its reliability

Selected results are presented of the Traffic Study, one of 12 studies conducted by San Diego State University for the I-15 Congestion (Value) Pricing Project in San Diego, a 3-year demonstration. The focus is on the projects impact on travel times and their distribution on both the main lanes and the express lanes of I-15 for both ExpressPass and FasTrak phases of the project. Specifically addressed is the issue of reliability of on-time arrival enjoyed by the FasTrak subscribers and the high variability of travel times for the I-15 travelers who use only main lanes of I-15 for their commute. Examination of the ramp and freeway delays shows that in the worst-case scenario, FasTrak subscribers who use express lanes can save up to 20 min avoiding delay on the I-15 main lanes. This finding agrees with the drivers’ perceptions about their time savings when using FasTrak. Travel-time changes during the duration of the project also are examined. There were substantial year-to-year changes in travel times along the I-15 main lanes and the I-8 lanes used as control. The travel-time profile along the I-15 main lanes differed significantly from the profile along I-8, the control corridor, in both a.m. and p.m. peak periods.

SAN DIEGO'S INTERSTATE 15 CONGESTION PRICING PROJECT: TRAFFIC-RELATED ISSUES

Traffic-related findings from the evaluation of the Interstate 15 (I-15) congestion pricing project are summarized. The project was a 3-year demonstration that allowed single-occupant vehicles (SOVs) to use the existing I-15 high-occupancy-vehicle (HOV) lanes, known as the I-15 express lanes, for a fee. San Diego State University conducted an independent, multielement evaluation of the I-15 pricing project to assess its impacts for both the ExpressPass and FasTrak phases of this demonstration. The primary project goals were (a) to maximize use of the existing I-15 express lanes, (b) to test whether allowing solo drivers to use the express lanes’ excess capacity could help relieve congestion on the I-15 main lanes, (c) to fund new transit and HOV improvements in the I-15 corridor, and (d) to use a market-based approach to set tolls. At the end of 1999, the I-15 pricing project was meeting its primary objectives. There was substantially better utilization of the express lanes. Both ExpressPass and FasTrak were feasible solutions for generating sufficient revenue to fund the new express bus service, called Inland Breeze. Neither ExpressPass nor FasTrak negatively affected carpool volumes on the express lanes; FasTrak was able to redistribute volumes from the middle of the peak to the peak shoulders. Free-flow conditions were maintained at virtually all times. The project’s primary benefit was the reliability of ontime arrival for users. The project was also able to slightly alleviate congestion on the I-15 main lanes. SOV violation rates in the I-15 express lanes remained substantially below the preproject level. Also discussed are the air quality, delay, and park-and-ride impacts of the project.

Dynamic Value Pricing as Instrument for Better Utilization of High-Occupancy Toll Lanes: San Diego I-15 Case

Selected results are presented of the Traffic Study, one of 12 studies conducted by San Diego State University for the I-15 Congestion (Value) Pricing Project in San Diego, California, a 3-year federal demonstration that converted underutilized high-occupancy-vehicle (HOV) lanes into a high-occupancy toll (HOT) facility. The studies addressed traffic and traveler-related aspects, as well as economic, equity, and public relations issues. The Traffic Study constituted the core of the evaluation effort. One of the projects main objectives was better utilization of the express lanes to carry more traffic during peak commuting periods. This study examines the possibility that dynamic, traffic-sensitive value pricing, represented by the FasTrak phase of the project, is uniquely suited to improve both utilization and volume distribution during peak periods while effectively controlling level of service on the facility. Measures of utilization and volume distribution were defined and studied in spring and fall waves of the study. The study confirms statistically significant improvements in both peak-period utilization and volume distribution across the study waves. The results strongly suggest that the FasTrak programs dynamic fee structure was able to create desirable redistribution of a portion of express lane traffic from the middle of the peak to the shoulders. The fixed-fee structure of ExpressPass, the preceding program, was not able to create such redistribution. Despite the steady increase of express lane volume during the entire 3-year demonstration, the comfortable level of service C required by law was maintained at virtually all times.

SAN DIEGO'S I-15 VALUE PRICING PROJECT: IMPACT ON LOCAL BUSINESSES

This article presents findings of the Interstate 15 (I-15) Congestion Pricing Projects Business Impact Study conducted by San Diego State University over the projects 3-year duration. The ExpressPass and FasTrak programs offered drivers of single-occupant vehicles the use of I-15 Express Lanes to achieve faster and more reliable travel along the corridor. The Business Impact Study was designed to assess whether businesses recognized and valued the ExpressPass/FasTrak option. Delivery-based businesses or businesses located along I-15 were more likely to perceive themselves as highly dependent on employees or goods and services traveling the corridor. Such businesses were also more likely to regard the ExpressPass/FasTrak program as important and as having a positive impact. The I-15 FasTrak program ranked substantially lower in importance as a factor affecting business performance than such primary factors as supply of goods and labor, price of certain commodities, and tax levels and policies.

Peak Period Use of I-15 Corridor in San Diego, California: Long-Term Impact of FasTrak Program

The results of the 1998 to 2008 peak period monitoring of a 8-mi FasTrak section of Interstate 15 (I-15) in San Diego, California, are reported in this paper. The paper examines changes in peak period utilization and volume distribution throughout the peak with the emphasis on the level of service (LOS) offered on both high-occupancy toll (HOT) lanes and the main lanes of I-15. The study revealed that the peak period volumes on the HOT lanes (both FasTrak and carpool) strongly depend on the LOS deficit on the main lanes. Carpool participation was not hurt by the growing FasTrak volumes. The law-mandated LOS C was effectively protected by the dynamic pricing mechanism on the HOT lanes. The Congestion Pricing Project in San Diego proved able to redistribute a portion of the peak period volumes on the HOT lanes from the middle of the peak to its shoulders and now plays an important role in improving operation of the entire I-15 corridor.

Urban transportation modeling: The discussion continues

This article is a response to John Polaks article, entitled, ‘A Comment on Supernaks Critique of Transport Modeling,’ published elsewhere in this issue of TRANSPORTATION. It offers necessary clarifications to the issues discussed in an earlier article in this journal (Supernak, 1983). It also responds to the philosophical issues discussed in Polaks article, such as the nature of transport phenomena, and the role, form and methodology of transport modeling.