The evolution of public transit modes has been remarkable, fueled by the need for different transit modes to handle different demand levels, urban environment patterns, and natural constraints and barriers. One of these needs is the desire to overcome geographical and topographical barriers such as mountains, valleys, and bodies of water, which cannot be conquered by conventional transit modes without very large investments and changes made to the natural topography. Aerial ropeway transit (ART), a type of aerial transportation mode in which passengers are transported in a cabin that is suspended and pulled by cables, is one of the solutions to such cases. ART has its origins in aerial lifts that have been used for decades in Alpine ski resorts to transport skiers and tourists in cable-suspended cabins. The use of aerial transportation in the urban environment, which was once considered an unlikely possibility, has gained more attention worldwide, and it is now used as a public transit mode in several terrain-constrained urban areas around the world. This article describes the origins of aerial transportation and its advantages, components, service characteristics, available technologies, and applications around the world. The paper concludes with a fair assessment of the existing ART technologies.

To provide efficient public transportation services in areas with high demand variability over time, it may be desirable to switch vehicles between conventional services (with fixed routes and schedules) during peak periods and flexible route services during low-demand periods. This option is called variable-type services. Conventional, flexible, and variable-type service alternatives optimized for various conditions are compared to explore when variable-type bus services might be preferable to purely conventional or flexible service. The optimization models used for purely conventional or flexible service are adapted from previous studies. These models are integrated into a new model for optimizing variable-type bus service. The results of sensitivity analyses show how demand variability over time and other factors affect the relative effectiveness of conventional, flexible, and variable-type bus services.

This study is to evaluate the simulation-based and analytical-based methods for determining the left-turn lane queue storage length and deceleration length. Four traffic models were selected to estimate left-turn queue length, including analytical-based models [i.e., Highway Capacity Software (HCS+) and Synchro] and simulation-based models (i.e., SimTraffic and VISSIM). Recommendations were given on the basis of the accuracy levels and the costs of these models in terms of time. A simulation-based method for determining the required deceleration length was developed by using VISSIM. The results from this method were compared with different agencies’ guidelines, which were developed by analytical-based methods. A procedure is recommended in this paper for estimating the total left-turn length on the basis of the estimated queue storage length and the deceleration length.

Air transportation has an overall outstanding safety record. However, accidents do occur. If an aircraft is unable to stop within the runway length, the incident is described as an overrun. To provide passenger safety during an overrun, the Federal Aviation Administration (FAA) requires airports to have a 305 m (1000 ft) runway safety area. At airports that are unable to satisfy this requirement, because of either natural or man-made barriers, the FAA allows the use of a shorter runway safety area with a properly designed arrestor bed. A sensitivity analysis is presented in this paper to investigate critical parameters in the design of an engineered-materials arrestor system (EMAS). A single arrestor-bed configuration is used as a base case for considering a low-density concrete EMAS material. Five aircraft types are considered, ranging from 51,700 kg (114,000 lbs) to 322,100 kg (710,000 lbs) maximum-certificated takeoff weight. These aircraft types include aircraft with various landing-gear configurations. Earlier studies by the authors showed, on the basis of an analysis using B727 and B747 aircraft, that aircraft stopping distance is most sensitive to aircraft weight. This paper investigates a larger suite of aircraft types with a range of weight and main-gear configuration. Stopping distance in this study reflects a critical scenario of zero reverse thrust and minimal tire-pavement friction. In addition to the base-case analysis, additional studies are included to illustrate the dependency of stopping distance on arrestor-material compressive strength and arrestor-bed configuration.

Curb bus-only lanes and median bus-only lanes are two commonly used types of the on-street running ways of bus rapid transit (BRT) systems. Transit signal priority (TSP) has proven viable in improving transit schedule adherence and in expediting transit service and is recognized as a key element of BRT systems. From a TSP designer’s point of view, it provides a systematic analysis of the impact of bus-only lanes location on the development and performance of the logic rule-based bus rapid transit signal priority (BRTSP). As an emerging active TSP for use at isolated signalized intersections, BRTSP is centered on five categories of logic rules and can fully accommodate the variety of phase scheme. Green extension, early green, and phase insertion can be provided to prioritized vehicles within specific priority windows. The signal operations on bus-only lanes and general-purpose lanes are influenced by prioritized vehicle arrivals and departures and general traffic demands that are detected. Compared with curb bus-only lanes arrangement, median bus-only lanes arrangement imposes more restrictions on the establishment of phase combinations and phase sequences, resulting in less flexibility in assigning right-of-way at an intersection level. Among the components of BRTSP, the bus-only lanes location influences the first minimum green time calculation for vehicle phases, the walk interval calculation for pedestrian phases, the definition of priority windows, the design of logic rules, and the placement of prioritized vehicle detectors. The results of simulation experiments conducted by VISSIM under heavy load scenarios indicated the following: (1) no matter the bus-only lanes location, the phase sequence with all the through-vehicle phases defined as the initial phase had the potential to better moderate the negative effect of signal priority treatments on general traffic and pedestrians; (2)  insufficient evidence could not prove that median bus-only lanes arrangement had an overwhelming advantage over curb bus-only lanes arrangement in reducing the delays of prioritized vehicles at traffic signals and vice versa; instead, more attention should be paid to general traffic and pedestrians performance when arranging and managing the bus-only lanes; and (3) curb bus-only lanes arrangement appeared to have an advantage over median bus-only lanes arrangement in improving overall intersection performance if green extension and early green were provided to TSP-enabled intersections. To keep general traffic and pedestrians performance from severely deteriorating, phase insertion service, if desired (in addition to green extension and early green), should be provided only to intersections with median bus-only lanes in a conditional manner.

Pervious concrete pavement (PCP) has the potential to provide significant technical, economical, and environmental benefits. To better understand the beneficial impacts of PCP, its performance must be comprehensively evaluated and quantified. To evaluate the PCP performance, its pavement condition should be assessed. The primary aim of this research is to evaluate the PCP condition through incorporation of an adequate panel rating method. Two panel rating methods are evaluated for this purpose: visual digital inspection and in situ inspection. Field investigations are also conducted to record the surface distresses by describing their severity and density using the Ministry of Transportation of Ontario protocol. Finally, a model is developed and validated which relates mean panel rating (i.e., surface distress rating) to a pavement distress. It is concluded that the only significant variable (i.e., distress) in this model is raveling.

Pavement overlay is the most efficient form of material sustainability in road rehabilitation. In the United Kingdom and, perhaps, in most countries there is no standard approach for calculating the residual life of an existing pavement that can then be used to calculate the required overlay thickness to cope with future traffic loading. This paper will discuss the process for determining most of the important parameters used in overlay design. These parameters are traffic loading, layer thickness, stiffness modulus, interface condition, and fatigue properties. The discussion is aimed at critiquing the practice in the evaluation of these parameters by many designers. The paper draws attention to the common practices and methodology in the United Kingdom. It may not present a full rational approach but will certainly enhance the thinking in the field.

In practice, it has been observed that the method of pervious concrete void maintenance depends on which machines or vehicles the owners have available. This research compares the abilities of three common municipal utility vehicles—a vacuum truck with a flexible, 200-mm (8-in.) hose; a vacuum street sweeper; and a regenerative air street sweeper—to remove clogging material from the voids of in-service pervious concrete pavements. By using optical microscopy, it was found that clogging materials rarely migrate into voids deeper than 12.7 mm ($1/2\mathrm{in}.$) from the surface. Furthermore, all three machines were able to remove clogging materials that were located within 3.18 mm ($1/8\mathrm{in}.$) of the surface. The clogging material that was located deeper than 3.18 mm ($1/8\mathrm{in}.$) remained within the voids but was likely disturbed by either the suction or the forced air of the maintenance vehicles.

There is an urgent need to develop a system to quantify survey data quality and to study pavement performance characteristics with levels of confidence. To address this need, a system is proposed to quantify historical asphalt pavement condition survey data quality. The proposed confidence evaluation system uses the indicators based on asphalt pavement life-cycle characteristics. The resulting confidence levels of the indicators are used to determine the confidence level of the analyzed pavement’s life curves and performance characteristics. Twenty-three years of asphalt pavement condition survey data were provided by the Georgia Department of Transportation (GDOT) to validate the proposed system. The pavement’s life curves that have a high-confidence level can be obtained and used to analyze actual pavement performance; the average life of resurfacing effectiveness at a rating of 70 is approximately 9.4 years; this closely matches GDOT engineers’ assumption of 10 years of life, which is used for routine life-cycle cost analysis. The average project resurfacing time span, however, is 11.4 years, which indicates a 2-year lag for pavement preservation. More than 67 percent of the resurfacing projects are being delayed by more than one-year, indicating a serious problem. The derived load cracking propagation data indicates that this data can be used to support the development of reliable pavement life forecasting models.

This paper presents the results of the calibration and implementation of the Mechanistic-Empirical Pavement Design Guide (MEPDG) for the design of flexible pavements in Italy. Local input data for traffic, climate, materials, and subgrade (foundation soil) are evaluated and subsequently arranged, as required by the MEPDG to be used in the associated software. The coefficients of the distress models are derived by means of a comparison between the performances predicted by the MEDPG and those predicted by theoretical equations, which are believed to represent the local distress process of a pavement and/or assumptions prevalently made in Italy. A wide parametric analysis is performed so that the influence in design process attributed to load spectra, temperature, dynamic modulus of asphalt concrete, and resilient modulus of subgrade is shown. The results obtained from MEPDG are compared, according to the hypothesis of zero-maintenance during the service life of a pavement, to those derived from using a local mechanistic-empirical method. As a consequence, the difference between these two design methods is quantified. For a verification of the results obtained from the MEPDG, the 1993 AASHTO guide is used. Subsequently, by using the MEPDG for rehabilitation, a maintenance strategy based on two resurfacings of wearing course of pavement is also investigated, and its effect on the extension of service life of a pavement in contrast with zero-maintenance is shown. Therefore, this work provides the knowledge for locally implementing the MEPDG with significant success both for the assumption of zero-maintenance and resurfacing treatments during the service life of a pavement.

The falling weight deflectometer (FWD) is widely used for in situ nondestructive assessment of pavement layer moduli. For this purpose, FWD deflections are used with a number of back-calculation methodologies to come up with layer moduli. Back-calculating layer moduli from FWD deflections collected on thin asphalt concrete (AC) pavements is a challenge because the predicted deflection basin is not sensitive to the AC modulus. This study utilizes the portable seismic pavement analyzer (PSPA) to improve the reliability of back-calculated thin AC layer moduli. Compared with the FWD, the PSPA provides a direct measurement of seismic modulus at a higher load frequency level relative to the frequencies associated with typical truck traffic. Thus, the seismic modulus determined from PSPA tests needs to be corrected with the load frequencies typically used for pavement design. This paper compares AC moduli determined from laboratory dynamic modulus tests with corresponding values determined from FWD and PSPA measurements. The results exhibited favorable correlation between the AC moduli determined from laboratory and field tests at corresponding load frequencies and temperatures. The paper also proposes a methodology to obtain a composite modulus from mixture properties determined from laboratory tests of individual AC lifts for the purpose of comparing the composite modulus with corresponding values determined from field tests. The authors generated master curves of individual AC lifts on the basis of corresponding binder temperature–viscosity relationships and volumetric properties obtained from laboratory tests. A procedure was proposed for correcting PSPA AC seismic modulus at corresponding load frequencies and temperatures by using the master curves with Odemark’s assumption. This evaluation showed a promising correlation between the corrected PSPA modulus and FWD back-calculated AC modulus. From this, the authors provide a simple equation as an alternative method for correcting PSPA modulus when the material properties of individual layer are not readily available to employ the proposed methodology.

Remixing of the wearing course in the high-speed lane of a freeway resulted in a new road surface that, compared with the old surface in the adjacent low-speed lane, was perceived as a bumpy ride by road users, as well as by the road agency and the paving contractor. In this paper, the unevenness of the longitudinal road profiles of the old and the new (remixed) surfaces are analyzed and compared. The comprehensive analysis was conducted with statistical and signal processing tools. The probability density function (PDF), power spectral density (PSD), autocorrelation function, coherence, and occurrence of local obstacles in both lanes were evaluated and mutually compared. The profiles were quantified with commonly used indicators of road unevenness. The paper documents some disadvantages of the International Roughness Index (IRI) and advantages of road elevation power spectral density to reflect the ride quality of road profiles.

In traffic characterization, axle load spectra (ALS) are one of the most critical inputs in the new Mechanistic-Empirical Pavement Design Guide (MEPDG). Axle load spectra have a significant effect on predicted pavement performance and, thus, the design life. Typically, axle load spectra as measured by weigh-in-motion (WIM) systems are assumed to have adequate data quality and accuracy. In fact, the quality of WIM-based data has inherent uncertainties attributable to inaccuracy and systematic bias. Whereas WIM data accuracy depends on the sensor technology, calibration errors and drift over time may introduce a systematic bias. This technical note investigates the effect of axle load measurement bias on pavement design for flexible and rigid pavements. The results show that negative bias in axle load measurements significantly affects cracking performance for both pavement types. The bias is more critical for rigid pavements with thinner slabs. Therefore, a measurement bias limit of less than $\pm 5\%$ should be required to ensure that both flexible and rigid pavements have adequate design reliability against cracking. That the WIM scales be calibrated periodically to prevent a high negative bias is strongly recommended.