Michael Kyte

Effect of Weather on Free-Flow Speed

The effects of poor weather conditions on free-flow speed on a rural Interstate freeway are considered. It was found that free-flow speed is affected by pavement conditions, visibility, and wind speeds. It is also suggested that poor weather conditions occur with some degree of frequency in a number of U.S. cities and that the effects of poor weather should be considered in such cases as part of capacity and level-of-service analyses.

Implementing the maximum likelihood methodology to measure a driver's critical gap

This paper focuses on the implementation of the maximum likelihood technique to measure critical gap using data collected in the field. A methodology to define gap events is proposed, so that the accepted gaps and the largest rejected gaps could be obtained. The measurement at multi-lane sites and the treatment of major-street right-turn movement are specifically discussed. The paper points out some unusual situations where the proposed method cannot be applied directly. The proposed methodology has been used in NCHRP 3-46 to measure critical gaps under conditions in the U.S.A.

EFFECT OF ENVIRONMENTAL FACTORS ON DRIVER SPEED: A CASE STUDY

A case study on the effects of visibility and other environmental factors on driver speed was conducted as part of an intelligent transportation systems field operational test to reduce accidents caused by sudden changes in visibility levels. Baseline conditions established normal vehicle speeds for passenger cars and trucks. Reduced visibility and winds exceeding 40 km/h were found to be the primary factors affecting driver speed.

Including Exiting Vehicles in Capacity Estimation at Single-Lane U.S. Roundabouts

The current model used in the United States to predict approach capacity at a single-lane roundabout uses information about entry driver behavior in response to the circulating traffic stream only. There is no procedure for including exiting vehicles in capacity estimation. Exiting vehicles are vehicles that leave the circulating stream of traffic by maneuvering into the exit lane at a roundabout approach. Exiting vehicles are known to have an effect on capacity at roundabout approaches in other countries, but their effect in the United States is not known. The purpose of this research is to determine whether including exiting vehicles improves capacity estimation at a roundabout approach. An exploration of the relationships of the proportion of exiting vehicles and the width of the splitter island to approach capacities is included. Capacities were estimated both with and without exiting vehicles as part of the conflicting flow and compared with measured field capacities. The findings demonstrate that capacity estimates with exiting vehicles result in improved prediction of the actual capacity of a roundabout approach over estimates without exiting vehicles. The proportion of exiting vehicles in the major stream and the width of the splitter island appear to provide some benefit in capacity prediction, but exactly how these parameters can be incorporated into the capacity prediction process must be further explored.

Hardware and software considerations for implementing hardware-in-the loop traffic simulation

Digital computer simulation provides an important tool for the study of complex systems. When the complexity of the problem is too large to warrant an analytical solution, simulation is the only option to analyze system configurations or operational modes prior to their implementation in the field. Not all components in a complex system can be modelled in adequate detail in computer simulations: for example, only simple, generic models of traffic controllers are available. Real-time hardware-in-the-loop simulation allows real traffic controllers to interact with computer simulations to improve accuracy. This paper provides an overview of real-time simulation and then discusses hardware and software constraints to implementing a controller interface device (the NIATT CID II) for real-time hardware-in-the-loop simulation.

Hardware-in-the-loop real-time simulation interface software design

For years, traffic engineers have used traffic simulation software to develop, model, and test signal timing plans. However, before timing plans can be implemented in the field, they must be fine-tuned in an actual traffic controller operating under actual intersection conditions. Testing a signal timing plan in the field can cause minor or even major traffic disruption, creating delay and frustration for motorists and pedestrians alike. Real-time hardware-in-the-loop traffic simulation (HILS) can test timing plans in the office or lab rather than in the field. The controller interface device (CID) is the key component of the real-time simulation system. This paper provides an overview of real-time hardware-in-the-loop simulation and a discussion of the CID hardware design. Finally, HILS interface software design for three different simulation models (CORISM, VISIM, SimTraffic) is being explained.

A time-series analysis of public transit ridership in Portland, Oregon, 1971–1982

This paper examines the factors affecting changes in transit ridership in Portland, Oregon, during the period 1971 through 1982. A time-series methodology is used to investigate the effects of service level, travel costs, and market size at the system, sector, and route levels. Transfer function and multiple time-series models are compared. Intervention analysis is used to determine the impact of 81 service-level changes and 5 fare changes. A comparison is made of the elasticities estimated for these changes with elasticities developed from other studies.

Development of Knowledge Tables and Learning Outcomes for an Introductory Course in Transportation Engineering

Many decisions about the content of an introductory transportation engineering course are complicated by a wide range of topics and skills to be presented in a limited amount of time. The information presented in this paper was compiled by a working group of educators who represented universities of varying sizes and geographic areas. This working group was charged with developing core concepts and associated knowledge tables for the introductory transportation course for the following core concept areas: traffic operations, transportation planning, geometric design, transportation finance, transportation economics, traffic safety, and transit and nonmotorized transport. Instructors can weave the knowledge tables together by explaining the ways of being of a transportation professional and the course learning outcomes. A key focus of the working groups efforts was to provide more guidance to instructors on core content versus optional content. The intent of the working group was not to dictate what exactly should be taught in a course. The group therefore created more content than could fit into a typical semester-long course so that instructors would have flexibility. Some content should be viewed as more critical to the transportation profession than other material, and the working group will prioritize it accordingly. The objective of this paper is to demonstrate the work that has been completed and to get feedback from industry partners and other academic professionals about the curriculum. The efforts of the pilot studies over the next year will help determine the amount of time needed to cover the information in the knowledge tables.

SIMULATION-BASED STUDY OF TRAFFIC OPERATIONAL CHARACTERISTICS AT ALL-WAY-STOP-CONTROLLED INTERSECTIONS

Traffic operational characteristics at all-way-stop-controlled intersections were investigated by using AWSIM, a microscopic simulation model. The effects of vehicle arrival distribution and traffic volume split on intersection operations were studied. Traffic operations were analyzed from delay, capacity, and queue length perspectives. Empirical models were developed on the basis of simulation results for delay and queue length estimations. It was found that longer delays and queues resulted from platoon arrivals. Higher intersection capacity or lower control delay can be achieved with even volume splits on all the approaches. A generalized form of the delay model showed a better correlation compared with those for exponential-form models used by other studies. A nonlinear relationship was found to exist between the 95th percentile queue length and the average queue length. An empirical model was developed on the basis of the simulation results for estimation of the 95th percentile queue lengths. The model proves to be reliable and easy to use on the basis of field studies, and it fulfills one of the major shortcomings in queue estimation, which is currently unavailable in the Highway Capacity Manual.

Analysis of Traffic Operations at All-Way Stop-Controlled Intersections by Simulation

All-way stop-controlled (AWSC) intersections are one of the common intersection types in the United States. Although significant research has been completed on signalized intersections and two-way stop-controlled intersections, a limited number of studies have been made of traffic operations at AWSC intersections. In addition, although a general analytical procedure now exists for AWSC intersections, it is not capable of handling the wide variety of conditions typically faced by the practicing traffic engineer. Further, it may not be computationally possible for an analytical model to handle the large number of vehicle interaction combinations that exist at AWSC intersections. This study presents a new AWSC simulation model and some of the results from that simulation. The model was tested against the field data collected during NCHRP Project 3-46, Capacity and Level of Service at Unsignalized Intersections. The model can be used to predict vehicle delay, queue length, and saturation headways, which have ...