Click for next page ( 94

The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement

Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.

OCR for page 93
Conclusions and Recommendations 93 Congested urban corridors on which because of terrain such as grades and other system con- figurational issues, there may be safety problems due to truck-auto operational conflicts. Implementation of truck-only lanes along these corridors would provide significant levels of safety and reliability benefits in addition to travel time savings from diversion of trucks from the general purpose lanes. Urban corridors serving as key access routes to major freight facilities (such as seaports) where high truck and auto volumes, in addition to causing congestion, may be leading to reliability problems for international goods movement supply chains relying on the corri- dor for truck shipments. Along these corridors, the implementation of truck-only lanes would not only relieve congestion on the general purpose lanes (by diverting trucks), but also provide dedicated lanes for port truck traffic, resulting in improved truck freight mobility and reliability. 5.3 Proposed Research Program Although it would be desirable to have substantially more empirical data from which analyses of different truck-only lane concepts could be assessed, there appear to be opportunities to do addi- tional analysis of these concepts in the absence of real-world applications. A research program to conduct these analyses would have the following three major components: Experimental research. This research would set up temporary truck-only lane situations in order to collect empirical data that can be used to better calibrate models and conduct safety and travel speed studies. Screening studies, market-based studies, and development of concepts of operation. This research would use the existing studies to establish screening criteria for identifying high- priority intercity and urban corridors. For several high-priority corridors of each type, detailed procedures would be used to develop concepts of operations and evaluations of performance and cost-effectiveness. Simulation studies. These studies would use mesoscale traffic simulation models to detail corridor operations and estimate potential benefits of truck-only lanes in terms of improved safety and reliability due to truck-auto separation. 5.3.1 Experimental Studies One of the biggest disappointments of this study is the extremely limited real-world application of truck-only lanes from which to draw data for performance evaluations and B-C analysis. This is a particular shortcoming with respect to safety and reliability evaluations. This could continue to be a shortcoming until some truck-only lanes are actually built. However, there are some experi- mental programs/models that could be implemented on a limited scale that could begin to pro- duce the types of data that would greatly improve the state of knowledge. Experimental work could focus on identifying opportunities to convert existing separated lanes (or lanes on existing roadways that could be run as separated lanes) to truck-only lanes for a lim- ited time and run these lanes within a variety of operational configurations in order to gather eval- uation data. Some precedent for how this could be done can be drawn from the U.S.DOT Urban Partnership Agreement60 (UPA) program, and other congestion pricing experiments. In some of these cases, existing HOV lanes are being converted to HOT lanes or other types of variable pric- ing configurations. These same lanes, transitways, or new rumble strip separations could be con- verted to truck-only lanes for short periods of time and data on crash rates, recovery times, speeds, 60 See

OCR for page 93
94 Separation of Vehicles--CMV-Only Lanes and other types of performance issues could be collected. NCTCOG did a study on truck lane restrictions several years ago that could also serve as a model for this type of experimental work. Detailed observations could be made of differences in travel times for trucks and autos operat- ing on mixed-flow and truck-only lanes, differences in crash rates, changes in ramp queues, and changes in near crashes. The NCTCOG study cost approximately $500,000 and was conducted over an 18-month period in two major corridors. This included agency staff time, an $180,000 consultant analysis for data collection and analysis, and other related services. In discussing the potential application of this concept to a truck-only lane experiment, staff at NCTCOG expressed some concern about how traffic operations would be managed in order to provide access and egress to/from the truck-only lanes. This could present significant safety issues if the lanes are in, or closest to, the median and access was directly from the mainline mixed-flow lanes. Direct dedicated access/egress to/from the truck-only lanes would be much safer but the opportunities for this type of experimental set-up are much more limited. 5.3.2 Long-Haul Corridor Program At the time of this writing, an ongoing study61 undertaken on behalf of FHWA is conducting FTN. 61 research on long-haul intercity corridors that addresses many of the ideas for future research pre- sented earlier in this chapter. This study did return to the initial list of priority corridors developed by the Reason Foundation and developed its own criteria for selecting a corridor that would be able to fill gaps in an existing LCV network. The analysis in this study will include a more detailed eval- uation of potential markets for LCV operation, estimates of potential toll revenues, truck/rail diver- sion estimates, and an initial B-C evaluation. The market for LCV operations used Freight Analysis Framework (FAF) commodity flow data, HPMS data, and other local data sources to identify the types of commodities and O-D patterns of trucks in various corridors that were logical candi- dates for LCV operations. Based on this analysis, the study selected the I-80/I-90 corridor from Chicago to Boston as a high potential candidate corridor. The FHWA study represents a logical next step in the analysis of potential truck-only LCV cor- ridors. If the FHWA study corroborates the findings of this study that truck-only LCV oper- ations in intercity corridors do have potential positive net benefits compared to the costs, additional research should be conducted focusing on the following elements: Using similar screening methods as those used in the FHWA study, select multiple corridors for more in-depth analysis. These corridors would include varying levels of investment needed to close gaps in the existing LCV network, different types of commodity flow patterns, and dif- ferent levels of movement through urban areas. Using FAF and potentially other commodity flow data sources, supplemented with detailed interviews of shippers and motor carriers, develop a much more detailed analysis of the types of commodities and markets that would be served with an LCV network. These data and HPMS would be used to develop a more refined estimate of potential usage levels. With the selected corridors, develop detailed concepts of operations to determine the most eco- nomical truck configurations to serve the selected markets, identify market nodes along the corridor, and develop a concept for consolidation/deconsolidation of loads and managing off- system movements of commodities. This would be useful in helping to refine concepts for locating a limited number of access/egress locations, as well as estimating the costs associated with off-system infrastructure and operations. 61 FHWA, Technological Challenges and Policy Implications for LCVs on Exclusive Truck Facilities: I-90 Gap Closing Scenario, Draft Evaluation Results.

OCR for page 93
Conclusions and Recommendations 95 Using mesoscale simulation models and national crash databases, estimate potential safety, reli- ability, and operational benefits of truck-auto separation. This would be used to make more accurate estimates of the impacts of truck-auto separation on travel times, reliability (e.g., vari- ability in travel times), and crashes. Develop more refined estimates of truck-rail diversion by providing estimates of com- modities and O-D pairs in the corridor for which rail and truck compete and applying rail- truck cross-price elasticities to estimate diversion based on estimates of total logistics costs by mode. Develop more detailed estimates of toll revenues by conducting routing/costing simulations. 5.3.3 Urban Corridors The potential benefits of truck-only lanes in urban corridors have much to do with the congested nature of these corridors, which also lead to safety and reliability issues. The demand for capacity within limited rights of way makes throughput a much more critical consideration than in long- haul intercity corridors. The analysis conducted for this study suggests that many of the studies of truck-only lanes that have been done to date have been unable to evaluate some of the critical dif- ferentiators of truck-only lanes as compared to other approaches to increasing capacity. This study did conclude that linkages between major nodes in a freight system, such as links between ports and off-dock intermodal yards or concentrations of warehouse and distribution centers, are the most likely to generate sufficient demand to support limited-access truck-only lanes, and at the same time result in significant performance benefits of truck-only lanes (including congestion mit- igation as well as efficiency and reliability benefits for international truck freight shipments). The FHWA study chose not to conduct an evaluation of truck-only lane concepts in urban areas and the focus on LCV operations is less critical in urban corridors. The study team recommends that future research conduct a more in-depth analysis of benefits and costs of urban truck-only corridors, focusing on the following key areas: A detailed time-of-day analysis of demand that includes both peak period and peak-period analysis of level of service to understand the impacts of differences in time-of-day distributions between auto and truck traffic on the viability of truck-only lanes. A traffic simulation of the operations of the facility to provide for more reliable estimates of travel time savings benefits of truck-auto separation. This analysis should be supplemented with improvements in applications of travel demand models to analyze truck-only lanes with regard to accounting for the variability in PCE factors as a function of truck mix (truck percent of total traffic volume), and corridor configurational issues (grades and number of lanes). Use of traffic simulation to estimate the reliability (variability in travel times) benefits of truck- only lanes. Revised estimates of crash rates under varying truck-traffic conditions (truck percent of total traffic), based on simulation modeling and historic crash rates.