Evaluating Alternative Operations Strategies to Improve Travel Time ...

SHRP 2 L11: Final Appendices
interest are properly understood and measured. When comparing results from studies based on
revealed preference data and stated preference surveys for HOT-lane facilities in Southern
California, Brownstone and Small (2005) observed that the stated preference surveys tend to yield
much lower results than the revealed preference data.
Revealed preference data from HOT-lane facilities have also been used to improve statedpreference
survey instruments, and vice versa. This has allowed researchers to create scenarios
reflecting realistic trip alternatives, thereby reducing measurement errors from respondent
perceptions, as these scenarios are more familiar to the respondents.
Passenger Travel Value of Time
Since the initial conduct of studies for value of time, the relationship between the value of time and
user income has been a well-established relationship. Waters (1992) conducted a literature review,
summarizing the research from the 1960s, 1970s and 1980s with regard to the value of time as a
percentage of the wage rate. Most of the studies reported the value of time to be between 40 and 50
percent of the wage rate for commuting trips and a much higher percentage (around 85 percent of
the wage rate) for intercity trips. Fewer value-of-time estimates were specific to leisure trips.
These estimates were highly variable—ranging from 35 percent of the wage rate to more than 200
percent of the wage rate. Consistent with the findings published by Waters, Small (1992) also
observed that the value of time with respect to user income varied from 20 to 100 percent of the
wage rate across different industrialized cities. Small found that a good estimate for the value of
time is roughly half of the road user’s hourly wage rate.
Miller (1989) also reviewed the value-of-time literature and suggested that the drivers’ value of
time is 60 percent of the wage rate and the passengers’ value of time is 40 percent of the wage rate.
Another finding reported by Miller is that the value of time is approximately 30 percentage points
higher in congested conditions as compared with free-flow conditions. Based on this finding,
Miller suggested that the driver value of time in congested conditions is approximately 90 percent
of the wage rate and that the passenger value of time in congested conditions is 60 percent of the
wage rate.
While it is unpleasant to drive in congested conditions, travelers may be choosing to travel during
peak periods because they place a higher value on their travel time and/or on the schedule delay
associated with departing at a less-congested time. If this were not the case, travelers could adjust
their departure time so as to travel during the shoulder times adjacent to the peak when congestion
levels are not as severe.
Observing travelers on the New Jersey Turnpike, Ozbay et al. (2008) found that the value of time
is higher during the peak period than the pre-peak and post-peak periods for both commuting and
for leisure trips. The peak period value of time was found to be $19.72 for commuting trips and
$17.16 for leisure trips. This value of time was approximately $2.00 higher (about 10% higher) in
the peak than the pre-peak and post-peak periods for both commuting trips and leisure trips, with
the exception of pre-peak leisure trips, which exhibited nearly the same value of time as peak
leisure trips.
The morning peak period has been found to be the time of day with the highest observed value of
time, consistent with the findings that travelers with inflexible schedules (such as work schedules)
have a higher value for travel-time reliability. Ghosh (2001) found higher values of time—$22.00
per hour (75 percent of the wage rate) for the morning commute period along the I-15 HOT lane
DETERMINING THE ECONOMIC BENEFITS OF IMPROVING TRAVEL-TIME RELIABILITY Page B-21