摘要:

A traffic simulation and a mode choice module are employed iteratively for the assessment of real-time mode shift for the reduction of traveler delay. When the modules are allowed to iterate to equilibrium under expected travel demand and network capacity, the resultant time-variant mode splits represent baseline or expected conditions. Weather or other effects may impact realized demand or capacity, however. Travelers assumed to have a trip planning user service may make mode choices based on predicted roadway trip times for their origin, destination, and time of departure. Travelers without the user service make a mode choice based solely on expected conditions. In application to a test network under predictable roadway capacity reduction, the framework demonstrates real-time mode shifting has significant potential benefits. User (real-time mode shifter) benefits and system travel time reduction are quantified for a range of potential market penetrations.

ISSN:1024-8072    

DOI:10.1080/10248079708903727

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

It is expected that the Intelligent Transportation Systems (ITS) of the future will involve communication between vehicles and the roadside. In designing these communication systems it is imperative that one has a sound and detailed understanding of radio-wave propagation in both short-distance roadside and complicated urban environments. In this paper we discuss the type of propagation models that are needed for ITS designers to predict system performance. This paper has approached this problem by examining the radio-wave propagation in the roadway environment over the range of distances and at frequencies that will have the potential to meet the needs of ITS. The requirements of the individual functions of ITS were taken into consideration in addition to what portions of the radio frequency spectrum will be available.

ISSN:1024-8072    

DOI:10.1080/10248079708903728

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The Intelligent Transportation System (ITS) relies heavily on data communications systems to link field equipment such as traffic sensors, changeable message signs and incident response vehicles with traffic operations centers. This paper has two main purposes. The first is to present a review of data communications concepts essential in the design of wireless modems for the ITS 220 MHz spectral allocations. The second is to propose an architecture for such modems which offers a spectral efficiency much higher than that available in current products. The new modem architecture is implemented using the combination of a digital signal processor, discrete electronics, and high level software. All sophisticated signal processing is implemented in software to provide both high performance and flexibility. The system forms an ideal testbed for the design of future enhancements and modifications to fit specific ITS applications. A prototype has been constructed and subjected to full bench testing. Preliminary field testing has been performed and more is in progress.

ISSN:1024-8072    

DOI:10.1080/10248079708903729

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Successful communication of traffic information to motorists. via intelligent transportation systems (ITS) is critical for improved safety and traffic flow in high risk areas such as work zones. The conveyance of pertinent, real-time information through variable message signs (VMS) technology is integral to ITS. The content of messages presented on VMS is especially important given that drivers must detect, comprehend, and translate signage information while being occupied to some degree with the task of driving their vehicle. A simulation experiment was conducted, using a prototype dual-task methodology developed to examine message content of VMS in work zones and to assess the effect of message type, display type, sign content, and repeated exposure to the signs on message comprehension and translation. Twenty participants (mean age = 25 yrs) viewed a computer simulation of a section of road leading to a work zone site that had VMS along the road side. Signs were of two message types (speed vs. time signs), three display types (two inexpensive; one with full text wrap-around and one with partial wrap-around; and one expensive matrix of three lines by eight characters flashed twice), two similar message versions. and a complete repeat for reliability in a 2 x 3 x 2 x 2 repeated measures design. The primary task required attending to a grid line in the rearview mirror and remembering which signal had appeared. The concurrent, secondary task was reading the message content of VMS that were optically expanding at a rate comparable to traveling at 111 kilometers/hour (70 mph). Questions regarding the grid line signal and sign comprehension and interpretation followed. The results support this methodology's capacity to evaluate message content of VMS, especially in an ITS context. Message type significantly affected comprehension of sign content and translation of the consequences of the information conveyed, but display type did not influence responses to time or speed signs. This suggests a potential for substantial savings from the increased use of inexpensive displays instead of full-matrix units. Future research should involve assessment of the validity of the computer simulation, in addition to testing behavioral responses to message content either with a follow-up on-road and/or driving simulation study.

ISSN:1024-8072    

DOI:10.1080/10248079708903730

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

ISSN:1024-8072    

DOI:10.1080/10248079708909997

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

ISSN:1024-8072    

DOI:10.1080/10248079708909998

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

ISSN:1024-8072    

DOI:10.1080/10248079708903732

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

ISSN:1024-8072    

DOI:10.1080/10248079708903726

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor