This paper presents an analysis of freeway traffic flows under congestion based on the principle of traffic dynamics, using the example of recurring congestion. Queuing and discharging mechanisms are analyzed using the fundamental concept of conservation of vehicles. These analysis results are applied for reviewing the two conventional macroscopic analysis tools, deterministic queuing analysis and shock-wave analysis. Comparative study results have demonstrated that (1) the two methods are fundamentally different from the traffic modeling point of view; (2) deterministic queuing analysis always underestimates the overall magnitude of delays compared to shock-wave analysis; and (3) the area between the demand and the capacity curves in a queuing diagram is analytically equivalent to total vehicle-hours of travel in congestion as opposed to the widely accepted total vehicle-hours of delay. The study results imply that the guidelines of the 1994 Highway Capacity Manual may result in the underestimation of congestion-related statistics. For the purposes of illustration and verification, a numerical example problem is provided.

Traffic volume and travel time data collected at a number of arterial roads in Singapore were used to analyze the speed-flow relationships for radial and ring arterial roads. A new travel time–density model was formulated by incorporating “minimum delay per intersection” and “frequency of intersections per kilometer” as model parameters. The appropriate values of these model parameters also were established. The adjusted R² value of this model was higher than those for the journey speed–density and running speed–density relationships. The free-flow speed and maximum flow values of the travel time–density model also fitted favorably well with field data compared with those of the journey-speed models. The radial road capacity estimates range from 835 passenger cars per hour per lane (pc/h/l) for segments with uncoordinated (unlinked) traffic signals to 905 pc/h/l for segments with proper signal (linked) coordination. Not much difference in estimated capacities is observed between linked and unlinked segments for ring roads. The capacity estimate for arterial roads is 890 pc/h/l.

Classical sight-distance problems involve the horizontal and vertical alignment of the road and stationary objects around the roadway that interfere with the motorist's view. Dynamic sight-distance problems concern the sight-distance situation engendered by “nonstationary” objects such as vehicles using the roadway. This paper discusses a theoretical approach for evaluating the operational effect of a dynamic sight-distance problem that is associated with unprotected left-turning traffic at intersections. Specifically, the problem discussed in this paper concerns the effect of left-turning vehicles on the gap acceptance of the vehicles in the queue. Sample test results indicate that the dynamic sight-distance problem considered here can result in larger critical gaps, and hence significantly reduce the capacity of left-turn movements at unsignalized intersections or signalized intersections with permitted left-turn signal phasing. A sensitivity analysis shows that the severity of dynamic sight-distance problems increases with the traffic intensity (i.e., the degree of saturation). The paper concludes that the critical gap value for unprotected left-turning traffic is not only dependent on the number of conflicting traffic movements, but it is also dependent on the traffic intensity and traffic composition (e.g., percent compact vehicles versus percent noncompact vehicles). These factors should be considered in determining reasonable critical gap values that can be used for capacity analysis of unprotected left-turn movements at traffic intersections.

Because of the tight constraints on many streets in urban areas, it is not uncommon to situate a bus stop upstream of a signal-controlled intersection without the provision of a proper bus bay or setback. For a single-lane approach, where the overtaking of a stopped bus at the bus stop is prohibited, the setup of such a bus stop would significantly affect the delay incurred by road users. It is believed that the delay in such situations depends on a number of factors, such as the distance between bus stop and stop line, traffic and bus flows, dwell time of buses and signal settings. In this paper, a simulation model for estimating the delay on an approach to a signal-controlled intersection with a bus stop upstream is developed. To test the reliability of the model, field surveys were conducted to validate the simulation model. A good agreement between the observed and simulation results was obtained. When the simulation model was used, a new delay formula was established and calibrated for use in the design of a signal-controlled intersection.

The capacity of left-turn movements at signalized intersections is sometimes increased by using two exclusive double left-turn lanes at the intersection followed by a reduction to a single lane after the turn is made. A typical application is the use of double left-turn lanes onto a freeway entrance ramp, where the right lane is dropped in advance of the merge area. The effectiveness of the “added” outside left-turn lane and downstream auxiliary lane depends on the amount of traffic using that lane. While equal distribution of traffic between a continuous and an auxiliary through lane would result in the greatest total capacity of this lane pair, traffic and geometric factors are usually such that this does not occur. The 1994 Highway Capacity Manual does not address intersection configurations with downstream lane reductions. This paper describes the development of a mathematical model, based on field data, which does predict auxiliary lane use for this intersection configuration.

One factor that can reduce a lane's saturation flow to less than ideal conditions is when turning vehicles share the lane with through vehicles. The slow discharge rate of the turning vehicles reduces the lane's effective saturation flow rate in direct proportion to the percentage of turn vehicles in it. A model is described that predicts this percentage and the resulting saturation flow rate of the shared lane. Based on the results of this research, it is believed that the proposed model accurately predicts the lane volume for any approach to a signalized intersection and the uncontrolled approach to an unsignalized intersection. The model extends previous models by incorporating a sensitivity to both left- and right-turn movements and the probability of a lane change into a closed-form solution. Some field data are used to validate the proposed model.

This paper concerns a discrete-time, link-based, dynamic user-optimal departure time/route choice model using the variational inequality approach. The model complies with a dynamic user-optimal equilibrium condition in which for each origin-destination pair, the actual route travel times experienced by travelers, regardless the departure time, is equal and minimal. A nested diagonalization procedure is proposed to solve the model. Numerical examples are then provided for demonstration and detailed elaboration for multiple solutions and Braess's paradox.

An inverse trip distribution-volume of link flow (T-V) equation is derived by the introduction of a new concept, the pass through coefficient. Based on this, a new approach to calculate OD trip volumes from the observed link flows is presented along with the calibration of the related factors.

This paper presents a model to predict the influence of traffic flow on the running speed of signalized arterials in Montgomery County, Maryland, while controlling for link length, the number of lanes, and route type. The model separates the changes to link running speed due to same-direction traffic and intersection approach delay from cross-traffic. It is found that flow has a small impact on link speed, each 1,000 v/l/h reduces speed by 4–8 k/h. Longer links have higher speeds, indicating that they more closely approximate free-flow conditions. Measures of intersection and link travel times are also compared. Although link running times exceed intersection stopped delay in general, total intersection delay (stopped and approach) exceeds the delay caused by same-direction traffic. This information can inform investment decision makers about roadway and intersection improvements.

This study examines the trip-chaining behavior of workers. It develops nine work-related trip-chaining patterns from the 1990 Nationwide Personal Transportation Survey data, based on the sequential link of activities occurring in a single day. The study finds that more than 60% of trips for work in urban areas represent complex trip-chaining patterns. Males are more likely to use a simpler work trip pattern than females. From the results of analysis of variance, there are gender variations between trip-chaining patterns in trip rates for nonwork activities, travel distance, and travel time. There are also significant gender differences in trip rates and travel resources in each trip-chaining pattern.

This paper develops a new method to examine the factors that influence driver's seat belt usage. A binary logit model of the driver's beliefs in the effectiveness of seat belts is first developed. The seat belt beliefs probability is then used as an input to a seat belt usage model. Unlike the traditional binary approach, this model is formulated using the ordered probability approach, which allows three levels of choices of seat belt usage (rarely, sometimes, and frequently). The seat belt usage model was estimated separately for urban (short) trips and rural intercity (long) trips using a survey of drivers (385 interviews) conducted in Amman, Jordan. The model results show that drivers with homes located in rural or suburban areas, female drivers, and old drivers strongly believe in the effectiveness of seat belts. The presence of children in the household, vehicle ownership, and serious accident involvement also positively influence seat belt beliefs. Seat belt usage is affected by trip type, distance traveled, past involvement in traffic accidents, time of buckling up the seat belt, and extent of seat belt beliefs. Seat belt usage varies with the type of environment (rural or urban). Although older drivers strongly believe in seat belt effectiveness, their seat belt usage frequency is higher for rural trips than for urban trips. For work driving, the usage frequency was lower for urban trips than for rural trips. However, for both trip environments, the usage frequency is influenced greatly by the seat belt beliefs. The empirical results underscore the appropriateness of the proposed seat belt usage model and provide more insights into the pertinent factors affecting seat belt usage.

Passenger demands on underground stations are always excessive and can cause severe congestion. The study of pedestrian behavior is particularly important in planning and design of the underground stations during peak hours. This paper reports an investigation on the behavior of pedestrians in choosing between escalators and stairways in Hong Kong Mass Transit Railway (MTR) stations during peak hours. Time-lapse photography surveys were conducted in six selected MTR stations to collect the relevant data. The travel time functions of the vertical pedestrian facilities have been calibrated and are used for developing the pedestrian route choice model. Service levels have been defined for the vertical pedestrian facilities based upon the service levels defined by previous researchers. It was found that the stairway capacities in the ascending and descending directions in the Hong Kong Mass Transit Railway stations are higher than in London Underground stations. It was also found that the pedestrians are more sensitive to the relative delays when using the vertical pedestrian facilities in the descending direction than in the ascending direction.

Polymer sewer pipe load carrying ability when deflected to 20% pipe deformation under parallel plate loading is used in industry as an index of pipe quality. New developments in limit states design also require the assessment of pipe response beyond the small deflection limits currently specified (between 5 and 7.5% change in pipe diameter). New material models recently developed to predict the nonlinear time-dependent response of high density polyethylene (HDPE) are used in a materially and geometrically nonlinear finite-element analysis to predict pipe response during the flattening test. Comparisons are made with test results for two different plain HDPE pipes. The new analysis permits good quality predictions of pipe response to be made at large deformations (20% vertical diameter decrease) where materially nonlinear polymer response occurs at crown, invert, and springline. Modeling permits pipe response to be evaluated under a constant rate of deformation, stress relaxation, and other load paths.