published journal article
published journal article
conference paper
published journal article
working paper
This paper summarizes the literature on the effectiveness of employee ridesharing programs. It provides the conceptual and empirical basis for our evaluation of AQMD’s mandatory ridesharing ordinance, Regulation XV. We review the literature on the following topics: 1) employee ridesharing behavior and attitudes, 2) relationships between workplace characteristics and ridesharing behavior, 3) impacts of public programs on ridesharing behavior and, 4) effectiveness of employer-based ridesharing programs. We begin with a brief introduction on the origins of the current policy interest in ridesharing and the development of Regulation XV.
working paper |
Jun 1989
working paper |
Nov 1991
working paper |
Jun 1991
working paper |
Nov 1988
working paper |
Sep 1991
conference paper
A novel distributed method for estimating a trip table in real time is described. The system is called “persistent traffic cookies” by analogy with the use of cookies by web servers to keep track of the current state of web browsers navigating a web site. The method uses traffic cookies placed on in-vehicle computers to maintain the state (current trip) of vehicles moving through the system. These cookies are persistent from day to day; taken together, they form a complete travel history for a traveler or vehicle. The method leverages the vehicles to store their own travel data and then physically do carry those data around the network. Advantages include scalability in both storage and computational effort as well as the unique ability to incorporate the travel behavior of individuals into real-time traffic predictions. A small-scale simulation is presented to illustrate the concept and its potential applications.
published journal article
A systematic evaluation of the performance and effectiveness of a field operational test (FOT) of an integrated corridor-level adaptive control system was attempted from fall 1994 through spring 1999 in Irvine, California. The FOT was conducted by a consortium consisting of the California Department of Transportation (Caltrans), the city of Irvine, and two private-sector consultants—National Engineering Technologies Corporation and Farradyne Systems, Inc., a division of Parsons Brinckerhoff—with the city of Irvine as the lead agency. The FOT was a cost-share funded by FHWA as part of the Intelligent Vehicle Highway System Field Operational Test Program. The FOT involves an integrated advanced transportation management system, which extends the capabilities of existing traffic management systems in the city of Irvine and in Caltrans District 12. The evaluation originally entailed both a technical performance assessment and a comprehensive institutional analysis. This report of the Irvine FOT does not constitute a technical evaluation because of the failure of any of the planned technologies to be successfully implemented in the field. Because of the extended time frame associated with the project and the significant range of technical and institutional issues associated with the development and eventual failure of the FOT, a summary of project development, institutional barriers, and lessons learned is provided.
conference paper |
Jan 2002
published journal article
Background: The accuracy of electronic health records (EHRs) for identifying postpartum depression (PPD) is not well studied. Objective: This study aims to evaluate the accuracy of PPD reporting in EHRs and compare the quality of PPD data collected before and after the implementation of the International Classification of Diseases, Tenth Revision (ICD-10) coding in the health care system. Methods: Information on PPD was extracted from a random sample of 400 eligible Kaiser Permanente Southern California patients’ EHRs. Clinical diagnosis codes and pharmacy records were abstracted for two time periods: January 1, 2012, through December 31, 2014 (International Classification of Diseases, Ninth Revision [ICD-9] period), and January 1, 2017, through December 31, 2019 (ICD-10 period). Manual chart reviews of clinical records for PPD were considered the gold standard and were compared with corresponding electronically coded diagnosis and pharmacy records using sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV). Kappa statistic was calculated to measure agreement. Results: Overall agreement between the identification of depression using combined diagnosis codes and pharmacy records with that of medical record review was strong (κ=0.85, sensitivity 98.3%, specificity 83.3%, PPV 93.7%, NPV 95.0%). Using only diagnosis codes resulted in much lower sensitivity (65.4%) and NPV (50.5%) but good specificity (88.6%) and PPV (93.5%). Separately, examining agreement between chart review and electronic coding among diagnosis codes and pharmacy records showed sensitivity, specificity, and NPV higher with prescription use records than with clinical diagnosis coding for PPD, 96.5% versus 72.0%, 96.5% versus 65.0%, and 96.5% versus 65.0%, respectively. There was no notable difference in agreement between ICD-9 (overall κ=0.86) and ICD-10 (overall κ=0.83) coding periods. Conclusions: PPD is not reliably captured in the clinical diagnosis coding of EHRs. The accuracy of PPD identification can be improved by supplementing clinical diagnosis with pharmacy use records. The completeness of PPD data remained unchanged after the implementation of the ICD-10 diagnosis coding.
conference paper
Activity-travel chaining involves an interconnected series of activities and associated trips that occur between a pair of anchors or primary activities. By this definition, activity-travel chaining includes both the attributes of activities (e.g., location, duration, activity type, etc.) and trips (e.g., schedule, distance, route, mode, etc.). Prior research suggests that activity-travel chaining propensity can greatly influence travel demand and its temporal distribution. With the motivation to support reliable travel forecasting and inform travel demand management strategies, we investigate the direct and indirect effects of activity-travel chaining propensity for three activity types on peak and off-peak motorized person miles traveled (PMT). To perform the investigation, we employ a structural equation modeling (SEM) framework with five mediator variables (i.e., travel time savings ratio, activity space area, average daily trips, non-motorized travel mode share, and transit share) to capture the indirect effects of trip chain propensity (as well as socio-demographic and land use) on motorized PMT. We also compare workers and non-workers by specifying and estimating separate models for each group. The results indicate that activity-travel chaining propensities increase peak-hour motorized PMT for workers and non-workers. Also, non-workers chain maintenance activities during off-peak hours to avoid conducting or traveling to these activities during peak hours. We also find significant effects of location characteristics and mediator variables on peak-hour motorized PMT that policymakers can leverage when formulating travel demand management strategies.
presentation
