Over the past four decades, the United States has invested heavily in highways and airport improvements, and in general has opted not to develop intercity passenger rail service. Over the same period, by contrast, Europe and Japan have committed large sums of money to developing high-speed guided ground transportation and building extensive new high-speed rail networks. The United States launched a high-speed ground transportation (HSGT) initiative in the mid-1960s and abandoned it in the mid-1970s. Now the Clinton administration proposes to support HSGT development, but the level and type of support remains to be worked out. This paper explores the prologue to and current prospects for HSGT development in the United States.

By hubbing at a few airports, airlines can maintain high levels of aircraft utilization and take advantage of the economies of aircraft size. Passengers also benefit in the form of increased frequency of service. However, increased aircraft operations at major hubs imply certain diseconomies that include congestion delay, increased workload on air-traffic controllers, noise, and pollution. Using a network equilibrium model, this study attempts to project the future structure of domestic networks and to discuss some policy implications. The results suggest that network hubbing will continue to persist as an important feature of air transportation, but in a multihub system. Unless expanded substantially, major hubs will suffer from escalated levels of delays and will become mostly traffic-generator airports instead of connecting and transfer points. Some implications to the concept of wayports, hub pricing, and the role of aircraft technology in relieving delays at major hubs are also discussed.

An econometric model is estimated for intercity passenger demand using postderegulation data. The model incorporates some quality-of-service measures as explanatory variables. These include flight frequency during peak and off-peak periods, aircraft size (i.e., number of seats), and travel time. The results suggest that demand is elastic with respect to airfare, and is highly dependent on flight schedule and travel time. It seems that frequency and route planning will continue to be challenges for the airlines, and that the solutions are very much market specific. They will depend on, among other things, the predominant trip purpose (business or nonbusiness), and the capacity constraints that affect the utilization of specific airports.

The appropriateness of the current space standards (occupancy rates) for airline check-in area design is discussed. Based on a study of passenger walking patterns at the two international airports in Montreal, it is suggested that the design standards recommended in the International Air Transport Association guidelines result in an oversupply of space, sometimes in excess of twice the required minimum. This is attributed partly to the definition of capacity and the lack of a formal procedure for treating items such as luggage, carts, and stationary passengers that impede movement. It is proposed that the design occupancy rate be determined by adjusting the maximum occupancy rate to account for the impedance. Maximum occupancy rate is derived according to the relationship between occupancy rate and walking speed of passengers without baggage or carts, whereas adjustment factors are computed along the same principles as the passenger-car equivalency factors used in highway capacity analysis. The standard equivalent passenger in the present case is defined as a stationary passenger without a cart, and the space required by moving passengers with and without carts is estimated relative to the standard passenger. Application of the technique is explained using a numerical example.

The objective of this paper is to investigate the effects of heavy vehicles in through lanes and in left-turn lanes. Headway samples of 1,320 passenger cars and 722 heavy vehicles were measured in the field. Average headways were calculated for traffic flows of all passenger cars and all heavy vehicles in through lanes and left-turn lanes, respectively. The results show that different adjustment factors should be applied for through heavy vehicles and for left-turning heavy vehicles in calculating saturation flow rates. The adjustment factors for left turns should also be differentiated in accordance with the percent of heavy vehicles in traffic flow. Almost all estimated adjustment factors were found to be less than the corresponding figures suggested by the 1985 “Highway Capacity Manual.” A revised procedure is recommended for evaluating traffic conditions in Taipei. Similar studies may be desirable for cities in other parts of the world to verify the validity of the current procedures.

A new methodology for predicting heavy-vehicle weight distributions and pavement loadings in terms of the governing weight limits and the intensity of enforcement is presented. Gross vehicle weight (GVW) predictive models are developed for defined reference truck types in two identifiable weight-distribution families under steady-state conditions. These models determine the probability of trucks operating at or less than a given GVW expressed as a percent of the prevailing weight limit and as a function of the intensity of enforcement of the governing regulations. A concept of truck substitution ratios is introduced to translate the predicted GVW distributions of the reference trucks into those of other truck types. The predicted GVW distributions are then converted into pavement loading on the basis of the weight split factors of the various axle units on the configuration. The methodology has strong predictive capabilities, with the models being stable both in time and space.

Calculations required for the design of a transition (spiral) curve are often facilitated by the use of tables that give the elements of the curve for selected values of length and minimum radius of the transition. The use of such tables can be dispensed with and the design done more simply by the use of a master curve called the unit curve. The elements of the unit curve are developed and listed in this paper. Every element (linear dimension) of a field highway transition, including the tangent distance, is obtained from the corresponding element of the unit curve as a multiple of the characteristic constant of the field curve. This characteristic constant is $2\mathit{RL}\text{,}$ in which R = minimum radius, and L = length of the transition. The design of a transition thus becomes a matter of picking up the listed values of the unit curve for the required elements and multiplying by the characteristic constant of the field curve. An example is included to explain the procedure.

Kansas State University conducted research for the Kansas Department of Transportation to evaluate their retroreflective sheeting policy. This paper presents a recommended methodology for conducting a life-cycle cost analysis using Kansas cost figures and bid prices for two sheeting types as an example. A 50-state survey uncovered only four states that had ever done an economic analysis of sign sheeting. All were old studies and none used life-cycle cost-analysis techniques. Three types of signs were analyzed. For a new overhead guide sign, signs with high-performance sheeting had an equivalent uniform annual cost (EUAC) of $206.27/sign/year versus $243.40/sign/year for signs with engineering grade sheeting. For overlaying an existing guide sign, the EUAC is $152.2/sign/year for signs with high-performance sheeting versus $178.8/sign/year for signs with engineering grade sheeting. For a ground mounted sign, the EUAC is $4.79/sign/year for signs with high-performance sheeting versus $6.95/sign/year for signs with engineering grade sheeting. It was concluded that Kansas policy of using signs with high-performance sheeting was cost-effective. These conclusions are not necessarily valid in other states, and only two materials were used in the example because valid cost figures were available on only two materials; however, the methodology could be used by all states with appropriate data. An analysis of life-cycle cost results made available by several states would result in a significant contribution to nationwide results on all materials used in the United States under actual conditions.

Stochastic queueing methods are often applied to highway systems to estimate performance characteristics such as delay and queue length. Inherent in stochastic queueing methods is the assumption that the system in question operates at steady state for the duration of the analysis period. The validity of this assumption with respect to traffic-flow facilities is, at times, in question. It is therefore somewhat surprising that the vast body of literature concerned with the application of stochastic queueing methods for the assessment of highway operation includes very little discussion on the relevance of the steady-state assumption. This paper presents a simulation-based methodology for evaluating the appropriateness of the steady-state assumption. The methodology is demonstrated using a particular type of highway facility—a two-lane highway work zone. Application of the methodology suggests that the assumption of steady-state operation may not always be reasonable and, as such, illustrates the potential need to investigate the steady-state tendencies of a facility type prior to exploiting stochastic queueing techniques.

A comparative analysis is made between the analytic hierarchy process (AHP) and the multiattribute value (MAV) functions, using the MAV theory as the basis of reference, in the evaluation of transportation projects. The analysis considers three different perspectives: theoretical support, practicality, and ability to capture the decision maker's (DM) preferences. From the theoretic-behavioral standpoint, it appears that the validity of some of the assumptions of the AHP remain to be formally established, as concluded by several researchers. Secondly, the practicality of AHP was analyzed, in terms of the quantity and type of information demanded from the DM. For an even mix of ratio scale variables and nonratio scale variables the AHP requires less information than the MAV, provided the number of alternatives is less than five. Beyond this limit, the AHP requires more information than MAV. The ability to capture the decision maker's preference structure is analyzed through a case study, to which both methods were applied. In this limited test, the DMs found the MAV theory was slightly closer to their preference structure, though they were not fully satisfied with the results of either model. In spite of this, both DMs declared satisfaction with the insights they gained from the process.

There has been an increased interest in the use of recyclable materials due to environmental and economic concerns. As a result, the use of recycled materials in roadside safety features is being explored. In the present paper, a guardrail post manufactured from recycled plastic and steel is evaluated for possible use along highways. Tests were carried out on two cross-sectional configurations. A static cantilever bending test shows that although the plastic posts have less stiffness and strength than a standard wooden post, their energy absorption is approximately three times as large as their wooden counterpart. The plastic posts behaved essentially as rigid elements and sustained no permanent damage in standard in-situ tests. A large pendulum was used to impact the posts in an in-situ condition, and also with a fixed base and a variation of post temperature. Comparison of performance with standard posts was favorable. Finally, a full-scale crash test using a 20-kN (4,500-lb) automobile traveling at 96 km/h (mi/h) and making contact at a 25° angle shows that the commingled plastic post and W-beam guardrail can successfully contain and redirect an errant vehicle.

This paper describes the concept, design, and prototype fabrication of an innovative four-bar mechanism-based wheelchair-lift system, which can allow a wheelchair-, scooter-, or walker-bound passenger to be lifted from ground level to the bus floor level and back again. The new lift is designed to accommodate a passenger service load of 3,300 N (750 lbf). It has relatively few components. It consists of two four-bar mechanisms, a platform, and two hydraulic actuators to raise, lower, fold, and unfold the platform. The use of restraining pins enables the lift platform to pivot normal to the ground for stowage. When stowed away, it folds into a very compact space. The lift is designed with safety, human comfort, and ride stability in mind. Under full load conditions, the angular deflection of the lift platform is 0.8°, as opposed to nearly 3° in existing lifts. The lift provides a very smooth ride to the passenger, without any uncomfortable jerking or vibrations. The device represents a sound alternative to existing lifts.

The application of elastic theory to the design of overlays on existing pavement requires that a modulus of elasticity be assigned to the existing structural system. Estimates of elastic modulus are obtained from dynamic deflection readings in the field; but asphalt is a highly temperature-sensitive viscoelastic material, and deflections not corrected to a standard temperature can produce misleading results. It is therefore the objective of the present study to develop a procedure for estimating an effective modulus of elasticity for a layer of asphaltic concrete in which a temperature gradient exists because of the combined influences of solar radiation, wind, air temperature, cloud cover, and other variables specific to time and location that cause temperature variations within the pavement layer. Two models are presented for the achievement of that objective. The first of the two models has been designed to utilize site-specific conditions for calculating a temperature profile at a given time within an asphaltic layer. The second model relates an equivalent elastic modulus to the calculated temperature profile.