Khattak, A., and D. Rodriguez, The impact of neo-traditional developments on traveler behavior,
Transportation Research, Part A: Policy and Practice, 39:6, 2005, pp. 481-500.

Although previous research has supported the view that neo-traditional or new-urbanist designs result in more
walking activity, several questions remain: Do residents of these neighborhoods substitute walking for driving
trips, or do they make more trips overall?  What is the role of self-selection of residents in these developments?
This paper aims to address these questions by examining differences in travel behavior in a matched pair of
neighborhoods (one conventional and one neo-traditional) in Chapel Hill and Carrboro, North Carolina.  A detailed
behavioral survey of 453 households and two-stage regression models suggest that single-family households in
the neo-traditional development make a similar number of total trips, but significantly fewer automobile trips and
fewer external trips, and they travel fewer miles, than households in the conventional neighborhood, even after
controlling for demographic characteristics of the households and for resident self-selection.  The findings suggest
that households in the neo-traditional development substitute driving trips with walking trips.


Anspacher, D., A. Khattak, & Y. Yim, The demand for rail feeder shuttles, Journal of Public Transportation,
Volume 8, No. 1, 2005, pp. 1-20.

Rail transit systems offer opportunities for travelers to avoid traffic congestion in large urban areas. This article explores
the possibility of expanding access to existing rail transit systems through demand responsive shuttles.  It examines
demand for such an innovation in the San Francisco Bay Area where relatively good rail service already exists.  Using
survey data collected in a case study of one urban and one suburban neighborhood (N=800 individuals surveyed) served
by the San Francisco Bay Area Rapid Transit agency, this article investigates the influence of several factors on people’s
willingness to use, pay for, and wait for the shuttles.  The results indicate that a significant percentage of the surveyed
population is willing to try the shuttle.  Higher willingness to use the shuttle was associated with women, younger and
elderly respondents, noncommuters who travel by SOV, and rail users who access the stations by transit.  Higher
willingness to pay for the shuttle was associated with suburbanites.


Khattak A., N. Rouphail, K. Monast & J. Havel, “A methodology for prioritizing and expanding freeway
service patrols,” Transportation Research Record, 1861, TRB, National Research Council, Washington, D.C.,
2004. pp. 1-10.

Freeway Service Patrols (FSPs), classified as part of Intelligent Transportation Systems, help enable smooth traffic flow
by aiding stranded motorists and assisting in incident clearance.  Many major urban areas currently have patrols, and
most medium-sized urban areas are following suit.  The success of FSPs has resulted in frequent requests for service
expansion.   The decision of where to put the next patrol is becoming more difficult because an assessment of greatest
need typically indicates that the high-priority areas already have the service, while the possible effects of the service are
often indistinguishable on lower-priority facilities.  In this paper, we develop a new approach that helps determine the
most beneficial locations for patrol deployment using expanded placement criteria.  North Carolina is used as a case
study.  Analysis of three incident/crash indices was combined with spatial analysis, incident type distributions, average
hourly freeway traffic volumes, and incident delay estimations to identify, evaluate, and compare FSP expansion candidate
facilities.  Results of the research have been incorporated into a decision-support tool that allows easy planning and
operational assessment of candidate sites by comparing performance values between sites, modeling the effect of
FSPs, and estimating their key potential benefits.  By using the tool, decision-makers can quickly assess the needs
of different facilities to make an informed, cost-effective decision as to where to implement the next service patrol.


Schneider R., R. Ryznar, and A. Khattak “An accident waiting to happen: A spatially-oriented methodology
that integrates perceptions into proactive pedestrian planning, Accident Analysis and Prevention, 36,
pp. 193–211, 2004.

There are about 75,000 pedestrian crashes in the United States each year.  Approximately 5000 of these crashes are
fatal, accounting for 12% of all roadway deaths.  On college campuses, pedestrian exposure and crash-risk can be quite
high.  Therefore, we analyzed pedestrian crashes on the campus of the University of North Carolina at Chapel Hill (UNC)
as a test case for our spatially-oriented prototype tool that combines perceived-risk (survey) data with police-reported crash
data to obtain a more complete picture of pedestrian crash-risk.  We use spatial analysis techniques combined with
regression models to understand factors associated with risk.  The spatial analysis is based on comparing two distributions,
i.e. the locations of perceived-risk with police-reported crash locations.  The differences between the two distributions are
statistically significant, implying that certain locations on campus are perceived as dangerous, though pedestrian crashes
have not yet occurred there, and there are actual locations of police-reported crashes that are not perceived to be
dangerous by pedestrians or drivers.  Furthermore, we estimate negative binomial regression models to combine
pedestrian and automobile exposure with roadway characteristics and spatial/land use information.  The models show
that high exposure, incomplete sidewalks and high crosswalk density are associated with greater observed and perceived
pedestrian crash-risk.  Additionally, we found that people perceive a lower risk near university libraries, stadiums, and
academic buildings, despite the occurrence of crashes.


Khattak A., and M. Rocha, “Are SUVs Supremely Unsafe Vehicles? Analysis of rollovers and injuries,”
Transportation Research Record, 1840, TRB, National Research Council, Washington, D.C., pp. 167-177, 2003.

With increasing speed limits and more light trucks penetrating the market, concern over their rollover risk is growing.
In particular, the general public and automobile manufacturers would like to know if the increasingly popular Sports Utility
Vehicles (SUVs) are indeed safer compared with other vehicle platforms.  This paper investigates how various vehicle
platforms influence rollovers and driver injuries.  Specifically, we explore: 1) the rollover intensity of SUVs vis-à-vis other
vehicle types in single-vehicle crashes and 2) the severity of the resulting driver injury.  A good quality federally maintained
database is used for crash analysis.  The database is a relatively clean stratified sample of police-reported tow-away
crashes nationwide and it contains detailed information about vehicle rollovers.  Rollover intensity, captured by the number
of quarter-turns, is investigated using weighted negative binomial models; injury severity, measured on the abbreviated
injury scale, is examined using weighted ordered logit models.  New insights emerge about the factors that increase
rollover intensity and injury severity.  As expected, SUVs are more likely to roll over and therefore injure their
occupant drivers more severely.  However, SUVs also protect their drivers during collisions due to their greater
crashworthiness.  In fact, the SUV crashworthiness effect exceeds the rollover effect, on average.  The implications
of these findings are discussed.


Khattak A., Y. Yim and L. Stalker, “Willingness to pay for travel information,” Transportation Research-
Part C, Vol. 11, No. 2, Pergamon Press, pp. 137-159, 2003.

Improved travel information received via electronic sources can inform people about travel conditions and help them make
travel decisions.  The personal benefits of high quality travel information may motivate individuals to pay for information.  This
study analyzes travelers willingness to pay for better quality information received from a traveler information system offered
through a public–private partnership in the San Francisco Bay Area.  The data were collected in 1997 through a computer-
aided telephone interview of individuals who called traveler advisory telephone system (TATS) and were willing to be
interviewed (N = 511).  The survey results indicate that the average number of times per month the respondents called
TATS was 4.80 (TATS was a free service at the time).  The average use of the system would decline if the service was not
improved but a service charge was initiated.  People indicated that they were more willing to pay for a customized service.
The impacts of travel information, travel context and socioeconomic variables on willingness to pay for information were
analyzed by estimating a random-effects negative binomial regression model of revealed and stated TATS calling frequency.
The results indicate that customized travel information, longer trips, work trips, and listening to radio traffic reports are
associated with higher TATS calling frequency and with greater willingness to pay for information.  Overall, the consumer
response to purchasing travel information services seems cost-sensitive and future efforts can focus on commercialization
of travel information, beginning with where demand for information is relatively inelastic and improvement or customization
of travel information is achievable.