Highway Lane Research Articles

Roadway Controller for Automated Highway System

In this paper a roadway controller is designed, analyzed and simulated for single automated highway lane which consists of vehicles equipped by cruise controllers keeping the desired safety distance which is made to depend on the following vehicle velocity. Main results of the paper are the following: Macroscopic traffic flow model for mean speed evolution which takes into account command speed generated by roadway controller; Roadway controller which provides the desired traffic density distribution in the presence of stream disturbances such that entrance and egress of vehicles. Results are confirmed by simulation.

Effects on roadside noise levels of sound absorptive materials in noise barriers

There is considerable interest in the use of sound absorptive materials for reducing noise reflected from noise barriers although there is little reliable information on their effectiveness in practice. The primary object was to determine, under carefully controlled measurement conditions, the effects on roadside noise levels of applying sound absorptive materials to the traffic face of noise barriers. Two sites were chosen where a modular type of noise barrier had been erected. At one site the road ran in a shallow cutting and 3.7 m high barriers had been erected on both sides of the road with a separation distance of 34 m. At the other site a single 3 m high barrier had been erected adjacent to an eight lane highway. At both sites the panels were of identical manufacture and were highly sound absorptive on the traffic face but reflective on the reverse side. Measurement of traffic noise were made close to the roads both behind and opposite the barriers with the panels in the normal position and then measurements were repeated after the panels had been reversed such that the reflective side faced the traffic. It was found that at both sites there was an increase of noise of generally less than 1 dB when the barrier face was changed from sound absorptive to reflective. ©

Variability of traffic-flow measures across freeway lanes

On most freeways, a number of factors interact to produce lane-to-lane variations in speed and volume which are both site and volume dependent. The following paper explores and statistically verifies these variations using detector data and a combination of complementary techniques based on data collected for 30 days at 27 detector stations in May 1994 along the Queen Elizabeth Way freeway near Toronto, Ontario. The analysis indicates that considerable volume dependencies exist at each site, and that these dependencies are site specific. In addition to their independent variations, speed and flow are also shown to interact differently across different lanes and result in different underlying speed-flow relationships. The findings are intended to be relevant to the calibration of microscopic traffic simulation models and automatic incident detection algorithms. As such, the paper does not attempt to specifically identify the underlying causes for the variations, but rather attempts to recognize the aggregated effects of these causes in a fashion that would be useful to real-time freeway traffic management system control strategies relying solely on loop detector inputs.Key words: traffic-flow theory, traffic modeling, traffic simulation, incident-detection algorithms.

Variability of traffic-flow measures across freeway lanes

Variability of traffic-flow measures across freeway lanes

An evaluation of freeway lane control signing using computer simulation

Lane control has been proposed as a traffic congestion alleviation method. For this method to work, a certain minimum percentage of the drivers must comply with the lane signing. The research described here has been performed to analyze the percentage of drivers that must comply with lane control. A simulation model was developed and tested. The simulation results for heavy traffic flow (1550 vehicles per hour per lane—vphpl), medium traffic flow (900 vphpl), and light traffic flow (300 vphpl) conditions indicate that lane control has little influence on congestion, regardless of the percentage of drivers that comply with the lane control signing. For heavy flow, the congestion level remains high even when all drivers comply. For medium and light flow, the congestion level remains low even when no drivers comply. The region between heavy and medium traffic flow is, however, sensitive to lane control. Four flow rates between medium and heavy flow were tested. The impact of lane control under these conditions is described.

Model-based tracking of complex innercity road intersections

Vision-based automatic driving along innercity roads and across complex innercity intersections requires to detect and track road markings and lane boundaries in order to determine the position and orientation of the vehicle relative to the ground. The complexity of intersection scenes and the disturbances in the detected contours enforce the use of model-based state estimation techniques. We recorded monocular image sequences of complex innercity road intersections from a moving small experimental truck in order to track intersection models using a Kalman filter. A scalar distance measure for the distance between image contour points and model edge segments turned out to be advantageous for the estimation process. This scalar measure is based on the simultaneous exploitation of edge element location and direction, thus using more information about the image gray value variation than previously when only the perpendicular distance between the edge element and the model segment was taken into account. We report about the theoretical foundation of this approach, its implementation and experimental results from several intersection sequences, as well as detailed comparisons with a previous, less sophisticated approach. These examples demonstrate the kind of problems which are likely to occur more frequently at intersection scenes than at those road scenes encountered while following a more or less straight, uninterrupted highway lane with clearly marked boundaries.

Vehicular Flow Past Incidents Involving Lane Blockage on Urban Roads: A Preliminary Exploration

The effects of freeway lane reductions on roadway capacity have been discussed in the literature, but only limited attention has been given to capacity reduction on urban arterial roadways. Videotaping of incident management on arterial roadways as part of another project made available data that could be measured and converted into headways. Fifteen incidents involving crashes and disabled vehicles from which measurements were drawn are examined in this report. All events blocked one lane on a four-lane urban arterial. From the data, headways were measured and estimates of vehicle flow rates computed. Overall, an incident blocking one of two lanes on an urban roadway will reduce the idealized flow from the 1,900 vehicles per hour per lane (3,800 vehicles per hour) as suggested in the Highway Capacity Manual by more than 60 percent for crashes and more than 50 percent for disabled vehicles. Crashes resulting in personal injury had a worse-case rate of 1,230 vehicles per hour, or 32 percent of capacity. The lowest recorded flow rate for disabled vehicles was 1,650 vehicles per hour, or 43 percent of capacity. Distribution of headways around crashes were substantially skewed. On the other hand, headways for disabled vehicles tended to cluster around the mean. Differences in headways not only arose from the type of incident but also appeared to be related to the amount of responder activity (e.g., one police officer versus multiple public safety responders) and by the cross-section of the roadway. In the latter case, roadways with painted medians had shorter headways than those with raised medians or painted center lines. More observations need to be made to validate these initial results.

Unjamming Traffic with Computers

This article discusses ways in which new computer simulation technology can help traffic engineers discover solutions to highway congestion. Specifically, a model of traffic scenarios called Transportation Analysis Simulation System (TRANSIMS), can be used to predict what the effects of building a bridge or adding a highway lane might be. The simulation also brings the scientific method to traffic planning; an experimental situation can be precisely re-created. Transportation planners are also learning from simulations by the Massachusetts Institute of Technology's Intelligent Transportation Systems Program. This system mathematically models behavior down to individual drivers habits--creating digital cars with a penchant for cutting off other cars, speeding, and showing traits seen often in Boston.

Traffic Density Control for Automated Highway Systems*

Traffic flow instabilities such as traffic congestion are often caused by ad hoc and inappropriate speeds and headways that humans choose when they operate their vehicles. In an automated highway system (AHS) environment, the driver's actions are replaced by those of a computer control system that is designed to optimize traffic flow. On the microscopic level, each vehicle is driven by a computer control system, which, based on the actions of the surrounding vehicles, sends the appropriate commands to the throttle/brake/steering actuators. On the macroscopic level, a roadway controller calculates the desired speed commands to be followed by vehicles in each section of the freeway lanes in order to achieve desired traffic density distributions that lead to optimum traffic flow conditions. In this paper, we design, analyze and simulate a roadway controller for an automated highway that achieves desired traffic densities along the lane. A macroscopic traffic flow model that is modified for AHS operation is used for control design and analysis. We show that the proposed roadway controller guarantees exponential convergence of the traffic density at each section to the desired density. Simulation results are used to illustrate the effectiveness of the proposed controller and the significant benefits AHS may bring to traffic flow. © 1997 Elsevier Science Ltd.

An Automated Highway System link layer controller for traffic flow stabilization

Controls for the link layer in the Automated Highway System (AHS) hierarchy proposed in the Partners for Advanced Transit and Highways (PATH) are developed. The link layer is modeled using vehicle conservation flow models. Desired traffic conditions on the highway are given by a pair of density and velocity profiles which are assumed to be consistent with the demand on, and the capability of, the highway system. The link layer control laws presented in this paper then stabilize the actual traffic condition to the desired values. Control laws are derived for three highway topologies: a single lane highway, a highway with multiple discrete lanes and a two-dimensional highway with an arbitrary flow pattern. The control laws obtained for each of the topologies is distributed and are suited for implementation in the lower levels of the AHS control hierarchy. Simulation results are also presented.

Microscopic modelling of freeway operations : Bunker, Jonathan, Ph.D. Queensland University of Technology (Australia), 1996. 456 pp. Supervisor: Rod Troutbeck

Microscopic modelling of freeway operations : Bunker, Jonathan, Ph.D. Queensland University of Technology (Australia), 1996. 456 pp. Supervisor: Rod Troutbeck

Implementation Elements for Conversion of General-Purpose Freeway Lane into High-Occupancy-Vehicle Lane

Conversion of a general-purpose freeway into a high-occupancy-vehicle (HOV) lane is an alternative to infrastructure addition for HOV system implementation. Research indicates that lane conversion is feasible technically if sufficient HOV usage and minimal main lane congestion occur from the first day of operation. The elements required for inclusion in an implementation plan for lane conversion to HOV after technical feasibility has been determined are presented. HOV-lane marketing is meant to heighten public awareness of the purpose and operation of HOV facilities while encouraging their use. The general public, local decision makers, and the local media are important elements to include in a marketing campaign for successful HOV implementation. These elements also apply to the successful implementation of lane conversion to HOV. Four HOV lane-conversion projects are investigated: (a) Santa Monica Freeway, Los Angeles, California; (b) Dulles Toll Road, Northern Virginia; (c) Interstate 90, Seattle, Washington; and (d) Interstate 80, northern New Jersey. The Santa Monica and Dulles projects are considered failures, whereas the Interstate 80 and 90 projects are considered successful. From these case studies and the literature review, implementation elements were identified: (a) technical feasibility, (b) early public outreach, (c) strong institutional arrangements, (d) inclusion of law enforcement agencies, (e) open relationships with the media, and (f) project opening timing.

Study of Speed-Flow Relationships on Individual Freeway Lanes

Many researchers have examined the form of the relationship between speed and flow on freeways. However, these researchers have concentrated on relationships for the freeway as a whole instead of on individual lanes. In this study, the relationship was examined for each of the three lanes at two locations on Highway 401 in metropolitan Toronto. It proved possible to accurately describe the mean speed in each lane with simple linear functions over the range of flows of most practical interest. Cubic functions provided comparable results over a wider range of flows, but it appears unlikely that the very high and very low flows are of sufficient interest to justify the added complexity. When an attempt was made to examine the relationship between speed and flow for the entire roadway, the linear functions were not adequate, but cubic functions performed reasonably well. However, the details of the full roadway curves are quite different from those of the curves described in the 1994 Highway Capacity Manual. In particular, the curves described in the manual are much steeper than the Highway 401 curves at high flows, implying a much more rapid loss of performance as flow approaches capacity than was observed. The full roadway curves are also surprisingly different from the curves for the individual lanes.

Adaptive/Variable Structure Control of Traffic Flow

Drastic deterioration of the traffic situation during the last years necessitates the development of roadway controllers which calculates the desired speed commands to be followed by vehicles in each section of the freeway lanes in order to achieve desired traffic density distributions that lead to optimum traffic flow conditions. In this paper the adaptive/variable structure roadway controller for automated highway system is proposed. The controUei is able to control the traffic flow under parametric uncertainty and eliminate the effect of stream disturbances. The design procedure is based on backstepping methodology and organising a sliding motion allows to make useful decomposition of variables that simplifies the control structure.

Link Layer Vehicle Flow Controller for the Path AHS Architecture

A link layer controller for the PATH AHS architecture is presented. A stretch of a multiple lane highway in which vehicles have different destination is considered. Using a principle of vehicles conservation, a partial differential equation model is derived. A velocity based controller that stabilizes vehicular density and velocity along the highway to predetermined profiles is proposed. Lyapunov techniques are used to ensure stability. Performance is illustrated by simulation results.

The effects of new high-occupancy vehicle lanes on travel and emissions

Many urban regions in the U.S. are planning to build extensive networks of new high-occupancy vehicle (HOV) freeway lanes. Past modelling efforts are reviewed and travel demand simulations by the authors are used to demonstrate that new HOV lanes may increase travel (vehicle-miles) and increase emissions when compared to transit alternatives. Recommendations are made for better travel demand modelling methods for such evaluations.

Evaluation of Crossover and Partial Lane Closure Strategies for Interstate Work Zones in Indiana

There are two main lane closure strategies for Interstate highway work zones, crossover and partial lane closure. Depending on the situation one or the other strategy may be more desirable. However, little research has been done to develop a systematic method for selecting appropriate lane closure strategies. The selection of appropriate lane closure strategies at Interstate highway work zones is discussed.

Tsing Ma Bridge, Hongkong

A major factor in Hong Kong’s extraordinary growth in recent years has been its strategic location on the Asia-Pacific Rim, where it acts both as a hub and an entrepôt to southern China. The whole project, known as the Airport Core Programme (ACP), consists of a large number of interlinking contracts. The centerpiece of the ACP is the Tsing Ma Bridge. This steel suspension bridge has a main span of 1,377 m, the longest combined road and rail span in the world, and a total length of 2,160 m. It spans the Ma Wan Channel, between the islands of Tsing Yi and Ma Wan, which provides the only access for ocean-going ships to the ports upstream. Provision is made for a dual three lane highway on its upper deck with twin single lane sheltered carriageways and twin tracks for the Mass Transit Railway Corp.’s Airport Railway on a lower deck.

Vertical Pavement Strain as Means of Weighing Vehicles

The concept of estimating vehicle loads by weigh‐in‐motion systems that monitor deflections in strain‐gaged bridges and culverts is well established. In this project, the possibility of estimating loads by monitoring subgrade deflections in flexible pavements was investigated. A line of vertical strain transducers was installed at a depth of 500 mm in a dense sand subgrade across one wheel path of the outside lane of a busy highway (this research was conducted in Australia, where the outside lane is on the left). The installation was calibrated with a truck of known weight, enabling the weights of other vehicles to be calculated and compared with weights determined by other means. Four test runs were conducted at six month intervals. Repeatability, sources of error, and accuracy of weight prediction are discussed. Successful results were obtained with the system, but further work would be required before it could be used as an operational system.

Automating Urban Freeways: Financial Analysis for User Groups

The automation of urban freeways is intended to reduce travel time costs, reduce direct (distance) costs, improve the safety of travel, create smoother vehicle operation, increase freeway lane capacity, and improve the comfort of travelers. This study performs a financial analysis of the first four of these effects of automation on present urban travelers by estimating the financial costs of automating vehicles (net of the savings on fuel and insurance), and calculating the break-even values for the speed increases needed to offset these costs. The analysis shows that automation will benefit heavy trucks and buses. Automation will also be cost-effective for auto commuters if large, but plausible, freeway speed increases can be obtained. Automation in the future (when nonautomated freeway speeds will be lower) will be beneficial for more users, since the break-even speed increases will be lower than their present values. The results of this analysis are very sensitive to assumptions regarding the cost of the automation devices and the changes in annual insurance payments.