Hot lane policies and their implications

This research examined the major changes in a corridor due to high occupancy/toll (HOT) lane implementation. This was accomplished by comparing the impacts of HOT lanes on three pairs of HOT lanes with similar design and operational characteristics. These pairwise comparisons of similar HOT lanes reduced the impact of exogenous factors and removed the issue of comparing HOT lanes that were so dissimilar it would be impossible to isolate the reasons for difference in results from the lanes. With strict registration requirements for free high occupancy vehicle (HOV) 3+ travel on the I-95 Express Lanes (ELs) in Miami there were indications that some carpoolers switched to lower occupancy modes. Tolled access for HOV2s on I-95 and the SR-91 ELs near Los Angeles resulted in lower usage of those ELs by the HOV2s as compared to most HOV lanes where HOV2 access is free. On the SR167 (Seattle) and I-25 (Denver) HOT lanes, exogenous factors like the price of gas and the economic recession seemed to be the primary influence on the usage of those HOT lanes. In both cases, carpool usage increased along with the price of gas. On I-25, the increasing unemployment rate coincided with a decrease in toll paying travelers. On SR 167 there were also indications of mode shifts among the transit, carpool and toll paying SOVs due to the fluctuating price of gas.     

Flight delays,capacity investment and social welfare under air transport supply-demand equilibrium

This paper analyzes benefits from aviation infrastructure investment under competitive supply-demand equilibrium. The analysis recognizes that, in the air transportation system where economies of density is an inherent characteristic, capacity change would trigger a complicated set of adjustment of and interplay among passenger demand, air fare, flight frequency, aircraft size, and flight delays, leading to an equilibrium shift. An analytical model that incorporates these elements is developed. The results from comparative static analysis show that capacity constraint suppresses demand, reduces flight frequency, and increases passenger generalized cost. Our numerical analysis further reveals that, by switching to larger aircraft size, airlines manage to offset part of the delay effect on unit operating cost, and charge passengers lower fare. With higher capacity, airlines tend to raise both fare and frequency while decreasing aircraft size. More demand emerges in the market, with reduced generalized cost for each traveler. The marginal benefit brought by capacity expansion diminishes as the capacity-demand imbalance becomes less severe. Existing passengers in the market receive most of the benefit, followed by airlines. The welfare gains from induced demand are much smaller. The equilibrium approach yields more plausible investment benefit estimates than does the conventional method. In particular, when forecasting future demand the equilibrium approach is capable of preventing the occurrence of excessive high delays.     

The value of travel time and reliability-evidence from a stated preference survey and actual usage

This research examined travel behavior of Managed Lane (ML) users to better understand the value travelers place on travel time savings and travel time reliability. We also highlight the importance of survey design techniques. These objectives were accomplished through a stated preference survey of Houston’s Katy Freeway travelers. Three stated choice experiment survey design techniques were tested in this study: Bayesian (D_b) efficient, random level attribute generation, and an adaptive random approach. Mixed logit models were developed from responses using each of those designs. The value of travel time savings (VTTSs) estimates do vary across the design strategies, with the VTTS estimates based on the D_b-efficient design being approximately half the estimates from the other two designs. However, among the three design strategies, the value of travel time reliability (VOR) was only significant in the D_b-efficient design.The estimated VTTS from actual Katy Freeway usage (as measured using actual tolls paid and travel time saved on the managed lanes) is $51/h. This likely also includes any value that travelers place on travel time reliability. In comparison, our combined estimate of VTTS and VOR based on the SP survey (D_b-efficient design) was $50/h, which is remarkably close to the estimate from the actual usage data. Based on our dataset, the D_b-efficient design technique proved superior to the other two techniques. Finally, this research also supports the importance of including both travel time and travel time reliability parameters when estimating the willingness to pay for, and therefore benefits derived from, ML travel.     

Assessing appropriate stiffness levels for spudcan foundations on dense sand

Before a jack-up can operate at a given location, a site-specific assessment of its ability to withstand a design storm during operation must be performed. During this assessment, the complex state of stress and strain under a spudcan is usually simplified to a value of foundation stiffness that is integrated as a boundary condition into the structural analysis. Soil stiffness is a critical parameter affecting the foundation and structural load distribution and displacements, and the jack-up natural period and dynamic response. The level of spudcan stiffness is an area of intense interest and debate. This paper assesses appropriate stiffness levels for numerical simulation. Utilising results from a detailed “pushover” experiment of a three-legged model jack-up on dense sand, the paper compares the experimental pushover loads and displacements on the hull and spudcans to numerical simulations using different assumptions of spudcan stiffness. These include pinned and encastré footings, linear springs and a force-resultant model based on displacement-hardening plasticity theory. Constant stiffness levels are shown to be inadequate in simulating the experimental pushover test. The non-linear degradation of stiffness associated with the latter force-resultant model is critical.     

Humpback Whales in Tonga: An Economic Resource for Tourism

The growth of whale-watching internationally has been spectacular. It now occurs in almost 100 countries and is estimated to be worth in excess of U.S.$1 billion each year in revenue. Thus, whales have become valuable as a resource for tourism. The Vava'u island group in the northern part of the Kingdom of Tonga in the South Pacific is an area with a growing reputation as a whale-watching destination. However, the industry is relatively new there and the impacts of whale-based tourism in these islands is, as yet, unknown. In addition, there has been a recent consideration of a return to hunting whales in Tonga. As a result, concerns regarding the value of these animals for tourism and the potential impact of a return to hunting have arisen. Consequently, a study was designed to provide a preliminary assessment of the economic impacts of these animals for the island community. This study estimates that humpback whales may be worth in excess of U.S.$700,000 annually as a tourism attraction and that there is significant potential for future growth. Furthermore, the study shows that current visitors are opposed to any resumption of whaling practices in the islands and that such a move would likely displace large numbers of tourists from Tonga. Thus, it is concluded that a resumption of whaling in Tonga would likely have a significant opportunity cost in terms of lost tourism revenues.     

An analysis of the retail and lifecycle cost of battery-powered electric vehicles

Regulators, policy analysts, automobile manufacturers, environmental groups, and others are debating the merits of policies regarding the development and use of battery-powered electric vehicles (BPEVs). At the crux of this debate is lifecycle cost: the annualized initial vehicle cost, plus annual operating and maintenance costs, plus battery replacement costs. To address this issue of cost, we have developed a detailed model of the performance, energy use, manufacturing cost, retail cost, and lifecycle cost of electric vehicles and comparable gasoline internal-combustion engine vehicles (ICEVs). This effort is an improvement over most previous studies of electric vehicle costs because instead of assuming important parameter values for such variables as vehicle efficiency and battery cost, we model these values in detail. We find that in order for electric vehicles to be cost-competitive with gasoline ICEVs, batteries must have a lower manufacturing cost, and a longer life, than the best lithium-ion and nickel–metal hydride batteries we modeled. We believe that it is most important to reduce the battery manufacturing cost to $100/kWh or less, attain a cycle life of 1200 or more and a calendar life of 12 years or more, and aim for a specific energy of around 100 Wh/kg.     

Intersection traffic energy management system (ITEMS): formulation and validation

Urban transportation and traffic face significant challenges as cities continue to grow. Traffic intersections present unique challenges for city planners. Several studies have proposed diverse approaches to managing intersection traffic. However, these typically fail to reduce both energy and trip time for all vehicles involved. This paper proposes the intersection traffic energy management system (ITEMS). By using speed regulation of two vehicles approaching an intersection on crossroads, ITEMS is able to resolve intersection conflicts. This obviates the need for either vehicle to stop. Two-vehicle and four-vehicle scenarios were simulated. It was found that ITEMS reduced the total energy about 22% and the trip time across the intersection by almost 16% for every scenario compared to a traditional fixed-timed traffic light intersection. ITEMS was also found to be superior than always giving a green light to urban transit vehicles. Furthermore, with ITEMS, the energy and trip time of each vehicle in the scenario was reduced when compared to other strategies.     

Volatility of car ownership, commuting mode and time in the UK

This paper has two objectives: to examine the volatility of travel behaviour over time and consider the factors explaining this volatility; and to estimate the factors determining car ownership and commuting by car. The analysis is based on observations of individuals and households over a period of up to 11 years obtained from the British Household Panel Survey (BHPS). Changes in car ownership, commuting mode and commuting time over a period of years for the same individuals/households are examined to determine the extent to which these change from year-to-year. This volatility of individual behaviour is a measure of the ease of change or adaptation. If behaviour changes easily, policy measures are likely to have a stronger and more rapid effect than if there is more resistance to change. The changes are “explained” in terms of factors such as moving house, changing job and employment status. The factors determining car ownership and commuting by car are analysed using a dynamic panel-data models.