Unreliable travel time is defined to mean a distribution of possible commute durations. This dissertation identifies occupational groups and shows how an individual's occupation can be expected to indicate how that person is going to behave in risky commuting stations.

Individual occupations attract a certain personality type. Also, individual occupations require different amounts of team work and pose idiosyncratic supervisory requirements for the employer. These effects create systematic variations among employer imposed work rules concerning employee's time use and employee expectations and reactions to the rules. The outcome is both personality driven and situation specific response to risky commuting situations.

A psychological construct -- locus of control -- draws a boundary between what an individual believes is influenced by her own actions and what is caused by factors external to her. A person with an internal locus of control is optimistic about her possibilities to influence the outcomes of risky situations, while a person with an external locus of control tends to see the cause of events as random or influenced by some powerful others.

Commuters with an external locus of control take fewer planned risks, reserving more slack time between planned arrival and official work start time. If something unanticipated throws them off the habitual path, they are less likely to go out of their way to maintain the planned arrival time. The commuters with more internal locus of control are more willing to take planned risks and are more committed to see that the risk pays off.

I use occupational classification developed by John Holland and resource exchange theory of Uriel Foa to establish a partial order from most external to most internal occupational groups.

The dissertation also includes models where the commuter trades off different elements of unreliable travel time: expected mean travel time, expected schedule delay early, and expected schedule delay late. Occupations affect these tradeoffs even when income and family composition are controlled.

Unreliable travel time is defined to mean a distribution of possible commute durations. This dissertation identifies occupational groups and shows how an individual's occupation can be expected to indicate how that person is going to behave in risky commuting stations. Individual occupations attract a certain personality type. Also, individual occupations require different amounts of team work and pose idiosyncratic supervisory requirements for the employer. These effects create systematic variations among employer imposed work rules concerning employee's time use and employee expectations and reactions to the rules. The outcome is both personality driven and situation specific response to risky commuting situations. A psychological construct -- locus of control -- draws a boundary between what an individual believes is influenced by her own actions and what is caused by factors external to her. A person with an internal locus of control is optimistic about her possibilities to influence the outcomes of risky situations, while a person with an external locus of control tends to see the cause of events as random or influenced by some powerful others. Commuters with an external locus of control take fewer planned risks, reserving more slack time between planned arrival and official work start time. If something unanticipated throws them off the habitual path, they are less likely to go out of their way to maintain the planned arrival time. The commuters with more internal locus of control are more willing to take planned risks and are more committed to see that the risk pays off. I use occupational classification developed by John Holland and resource exchange theory of Uriel Foa to establish a partial order from most external to most internal occupational groups. The dissertation also includes models where the commuter trades off different elements of unreliable travel time: expected mean travel time, expected schedule delay early, and expected schedule delay late. Occupations affect these tradeoffs even when income and family composition are controlled.

The 1990 amendments to the Clean Air Act mandated that local governments that violate federal ozone (urban smog) standards abide by a dizzying array of regulations, many of the most controversial of which--centralized state inspection and maintenance programs, carpooling requirements, zero- emission vehicle sales quotas, use of alternative fuels, and new-vehicle emission standards--are intended to control automobile emissions.

We present a simulation model designed to determine the impact on congestion of policies for dealing with travel time uncertainty. The model combines a supply side model of congestion delay with a discrete choice econometric demand model that predicts scheduling choices for morning commute trips. The supply model describes congestion technology and exogenously specifies the probability, severity, and duration of non-recurrent events. From these, given traffic volumes, a distribution of travel times is generated, from which a mean, a standard deviation, and a probability of arriving late are calculated. The demand model uses these outputs from the supply model as independent variables and choices are forecast using sample enumeration and a synthetic sample of work start times and free flow travel times. The process is iterated until a stable congestion pattern is achieved. We report on the components of expected cost and the average travel delay for selected simulations.