This paper presents a new methodology to measure delay at signalized intersections using linearly referenced global positioning system data. The methodology can be used to evaluate new models that estimate control delay (which includes deceleration delay, stopped delay, and acceleration delay). The main components of delay were determined by analyzing the distance-time, speed-time, and acceleration-time diagrams of a travel time run. The procedure used speeds and forward and backward acceleration algorithms to detect critical delay points. The stopped delay versus control delay relationship was found to be linear. In contrast to other studies, it was found that such a relationship did not pass through the origin and that a deceleration-acceleration delay value had to be added to the stopped delay term to obtain control delay. It was also found that deceleration and acceleration lengths were much longer than others reported in the literature and that the percentage of the control delay that takes place after the signalized intersection stop bar is not negligible.

Automatic incident detection on freeways is an essential ingredient for the successful deployment of Intelligent Transportation Systems. Several incident detection algorithms have been developed in the past three decades; however, most of them have not shown the anticipated performance in terms of detection rate and false alarm rate. Recently, the artificial neural networks (ANN) have been introduced to incident detection and shown success over the traditional algorithms. This study explores the application of two neural network models, namely, the Multi-Layer Feed-Forward and the Fuzzy ART algorithm. This study was conducted on the central corridor of I-4 in Orlando using real-world data collected via the traffic surveillance system. Different scenarios were considered to improve the performance and to capture the sensitivity of the developed algorithms to some factors. The study results showed that the Fuzzy ART algorithm has generally outperformed the Multi-Layer Feed-Forward network and California algorithms #7 and #8.

A new methodology for modeling delay at undersaturated two-way stop controlled intersections was developed. Total delay was divided into service delay and queue delay. Empirical models were developed to estimate service delay as functions of conflicting traffic volumes, and variance of service delay as a function of conflicting traffic volumes and the average service delay. These models were used as inputs to the Markovian (random) arrivals/generally distributed service times/one server model to estimate the queue delay. The Markovian (random) arrivals/generally distributed service times/one server model provided significantly better queue delay estimates than the Markovian (random) arrivals/Markovian service rate/one server model. The models were built based on 28 h of field data from eight intersections. The total delay model was also tested using data from another location. The proposed models estimate delays that are closer to the field data than the 1994 Highway Capacity Manual delay model. The new models are for unsaturated two-lane two-way approaches with random patterns and a major street speed limit of 48 km/h (30 mph).

This paper describes a method for automatic calculation of sight distance, subject only to constraints of horizontal geometry, along an arbitrary alignment of tangent sections, circular curves, and spiral transition curves. A parametric representation is used to describe the alignment and its tangent and normal vectors at all points. From this information, other parametric forms are derived that describe the curve along the center of the traveled lane and the lateral obstruction curve. Finally, an automatic method to determine sight distance is described, which is analogous to the manual “graphical method” often employed in practice. An example alignment is considered for demonstration purposes. The method is accurate, efficient, and consistent with manual calculations. It might be used for situations where detailed information about possible sight distance obstructions is not available, such as planning, preliminary design, or to support passing behavior modules of microscopic simulation models.

Achieving highway geometric design consistency is an important issue in the design and evaluation of rural highways to attain smooth and safe traffic operation. This paper presents a comprehensive literature review of highway geometric design consistency mainly on two-lane rural highways in North America and Europe. Previous research work on highway geometric design consistency is categorized into three main areas: (1) Speed considerations; (2) safety considerations; and (3) performance considerations. Speed considerations address the different effects of geometric parameters on the prediction of operating speed. Based on operating speed, design consistency of highway elements can be evaluated. Safety considerations explain the different relationships between highway safety and highway/traffic elements, vehicle stability, and low-cost improvements. Performance considerations address the different effects on driver workload, driver anticipation, highway aesthetics, and interchange design. Based on this review, a framework for highway design consistency is proposed, and recommendations for future research work on design consistency are suggested, including the need to develop operating speed consistency models based on 3D analysis.

Coordination of horizontal and vertical alignments is an important principle in road geometric design, and it should begin with preliminary design. Perspective drawings and sketches are considered to be effective means for evaluating this coordination. In the present paper, an approximate method is developed for the quick and adequately accurate drawing of the perspective of a road, and a relevant example is given. The method is based on the use of vanishing points and the properties of an equal-tangent parabola. It is assumed that the spatial curve of the centerline of a road element—defined as a road section along which the horizontal and vertical curvatures are constant—is an equal-tangent parabola. The proposed method does not substitute computer-aided drawing of the perspective, which is essential during the detailed design stage. It is nevertheless judged to be useful and more appropriate during the preliminary design stage, for it allows an engineer, designer, or researcher to reliably trace the perspective view of various horizontal and vertical alignment combinations and to obtain the desired coordination.

The objective of this article is to document the development of an automatic procedure for the routing of overweight vehicles with load-carrying and vertical clearance restrictions for the bridges of a highway network. The use of a network routing procedure within a geographic information system (GIS) operating in a PC environment is one of the distinctive features of the proposed approach. The procedure automatically identifies all bridges on a specified route and evaluates the adequacy of the bridge structures as well as vertical and horizontal clearance requirements for a given vehicle. A GIS computerized support methodology consistent with the Texas Administrative Code is developed. In particular, the proposed approach uses bridge load formulas to evaluate the adequacy of bridge structures for incoming overloads. Sample runs of the procedure using Texas data indicate that the procedure is computationally efficient.

By modeling a pavement structure as a beam rested on a viscoelastic foundation, we have constructed a physical picture linking together vehicle dynamics, road profile characteristics, and pavement response in a theoretical framework. Analytic expressions are derived for the vertical displacement, strain, and rate of strain of the pavement. The influence of surface roughness on these variables is investigated using actual road profiles. Furthermore, the rate of dynamic forces exerted on the pavement surface, serving as a deterioration indicator of pavement structures, is found to be linearly dependent on the energy-dissipation rate in the structure, for a reasonable range of the viscodamping constant of the structure. Because the dynamic strain can accelerate the appearance of fatigue cracks in pavement surface, its relation with lab testing the fatigue of a pavement specimen is also discussed. Although only a line dynamic loading is considered in the paper, the response of the structure under a loading with finite width can be derived by straightforward integration of the results presented in this study.

An alternative procedure for the determination of critical stresses and the thickness design of rigid pavements is presented. The effects of a finite slab size, different gear configurations, widened outer lane, tied concrete shoulder, second layer, and thermal curling are investigated. The well-known ILLI-SLAB finite-element program was used for the analysis. The program's applicability for stress estimation is further validated by reproducing very favorable results to the test sections of Taiwan's second northern highway, the AASHO road test, and the Arlington road test. Prediction models for stress adjustments are developed using a projection pursuit regression technique. A simplified stress analysis procedure is proposed and implemented in a user-friendly program (TKUPAV) to facilitate instant stress estimations at three critical locations of the slab; namely, the edge, corner, and interior. A modified Portland Cement Association stress analysis and thickness design procedure is also proposed and incorporated into the TKUPAV program. This program may be utilized for various structural analyses and designs of jointed concrete pavements in both the metric system and the U.S. customary system.

To facilitate applications of road penetration radar and other nondestructive testing technologies on roads, an apparatus was developed for the measurement of complex permittivity of construction materials. The system consists of an automatic network analyzer, a sample holder, coaxial cable connections, and data processing software. The sample holder can accommodate either laboratory-prepared or field-drilled asphalt and concrete samples with maximum aggregate sizes up to 19 mm and lengths up to 400 mm. A computer program is used to convert the parameters measured by the automatic network analyzer into the real and imaginary parts of the complex permittivity. The dielectric constants of 43 laboratory-prepared asphalt samples of fairly consistent bulk densities were measured over the frequency domain of 0.1 MHz to 1.5 GHz. The average dielectric constants were 6.0 ± 0.15 for dry specimens and 6.52 ± 0.99 for soaked samples over the frequency range of 8–900 MHz. A linear relationship was observed between the gravimetric moisture content and dielectric constant up to a moisture content of 1%, with dielectric constant increasing by 0.62 for every 1% increase of moisture content. The results indicate that the asphalt content and mix type did not significantly affect the dielectric constants, whereas the moisture content was identified as the predominant factor. The results provide much needed information on the dielectric properties of asphalt pavement materials.

The hot-air lance (HAL) is widely used in crack-sealing work based on the premise that it improves sealant adhesion. The effectiveness of the HAL in promoting adhesion is uncertain, however. Our goal was to measure the adhesion strength of bituminous crack sealant to dry asphalt concrete (AC) and assess the effect of the HAL on adhesion. To this end, we monitored the use of the HAL in the field and reproduced its effect on asphalt binders and AC pavements by using an automated HAL in a series of laboratory experiments. In those experiments, we looked at the effect of heat treatment on binder oxidation and embrittlement by means of infrared spectroscopy, thin-layer chromatography, and goniometry. We also compared the adhesion strength of three sealants applied to unheated, heated, and overheated AC substrates prepared with quartz or limestone aggregates. The results show that sealant adhesion and failure mechanisms are governed by the sealant source, the type of aggregate in the AC mix, and the heat treatment on the rout prior to pouring the sealant. The HAL does not oxidize the binder, but it may cause embrittlement by raising the asphaltenes content of the binder. Normal heat treatment has little effect on sealant adhesion to dry AC, but overheating can cause a 50% reduction in adhesion strength and lead to premature sealant failure. To retain the possible benefits of the HAL in sealing damp cracks and to prevent overheating, the HAL should be operated at reduced temperatures.

A precision offset spray system was developed for use by highway maintenance departments for the control of unwanted vegetation in the graded shoulder area adjacent to roadways. The offset sprayer consisted of two fundamental elements: (1) A machine vision system; and (2) a rapid response intermittent spray system. This study showed that it is feasible to use machine vision on a moving vehicle to automatically detect the presence of green plant material and to apply herbicides exclusively to plants and not to nonplant materials (e.g., bare soil). The system substantially reduced the amount of herbicide applied to nonplant material. In system tests, there was up to a 97% reduction in applied spray mix over conventional continuous spray applications with a plant deposition rate of 57% of continuous spray systems. Implementation of this technology would allow highway maintenance departments to reduce the cost of weed control and the amount of chemical herbicides released into the environment, while maintaining current levels of weed control efficacy.