Separation of Vehicles—CMV-Only Lanes (2010) / Chapter Skim
Currently Skimming:
Pages 78-95
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 78... ...
In addition, this chapter suggests some ideas for future research programs and analyses that go beyond what was feasible in this project. This study determined that there is substantial recent interest in applications of truck-only lanes in the following types of applications: • Long-haul intercity corridors, • Major urban corridors with high volumes of truck traffic, and • Major corridors providing access to ports and intermodal terminals.
|
From page 79... ...
The sections describing conclusions regarding applications of truck-only lanes also note where the current research and data are deficient with respect to the types of performance and B-C evaluations that need to be done, and provide ideas for how the underlying data and analytical methods can be improved. 5.1 Truck-Only Lanes in Long-Haul Intercity Corridors The primary motivation for developing long-haul intercity truck-only lanes includes the following: • Increase freight movement efficiency by increasing throughput and reducing travel times and delays for freight movement, • Provide improved freight efficiency at costs that are lower than the monetized value of the benefits, • Cost-effectively provide increased freight movement capacity in corridors with limited opportunities to expand rail mode or corridors without existing rail service, • Provide dedicated facilities on long-haul corridors for longer combination vehicle (LCV)
|
From page 80... ...
The Reason Foundation study also used a minimum truck volume threshold of 10,000 trucks per day to screen candidate corridors that would be viable (in terms of revenue generation potential) for the implementation of tolled truck-only lanes.
|
From page 81... ...
The analysis conducted in this study provides a framework for the estimation of total productivity benefits of LCV operations, which is based on an enhancement of the basic approach developed by the Reason Foundation, related to data inputs such as congestion and speeds. Conclusions and Recommendations 81
|
From page 82... ...
This can be attributed to savings along corridor segments close to, or along, the periphery of the Atlanta metropolitan area with notable peak period congestion. One of the deficiencies of current research on travel time benefits of truck-only lanes in longhaul corridors has to do with the inability of existing travel demand models to take into account the operational benefits of separating trucks and autos.
|
From page 83... ...
This observation would be useful in analyzing the viability of implementing truck-only lanes with LCV operations along long-haul corridors, based on a market analysis of the diversion potential of truck-only lanes. • The results from the B-C analysis very likely underestimate the benefits of truck-only lanes because they do not fully account for the safety benefits of truck-only lanes as compared with additional mixed-flow lanes.
|
From page 84... ...
technologies, and improved weight and safety enforcement of trucks. 5.2.1 Feasibility Criteria The feasibility of implementing truck-only lanes on urban corridors is a direct function of corridor demand and system characteristics, including truck and auto traffic volumes, share of truck traffic of total traffic, time-of-day variations in truck and auto traffic volumes and contribution of truck traffic to peak-period congestion, truck routing and O-D patterns, length of corridor, and number of lanes.
|
From page 85... ...
With respect to the application of truck lanes to reduce congestion on urban corridors, most of the analysis has been done with traditional travel demand models. All other features of truck-only lanes versus general purpose lanes being equal, the only way that truck-only lanes would compete favorably with general purpose lanes for congestion relief would be if trucks have a significant impact on congestion during the peak periods (periods with high levels of congestion)
|
From page 86... ...
On the other side of the balance sheet, travel demand models may underestimate the average travel time savings benefits to all motorists of having trucks and autos separated based on the way PCEs are calculated. There is evidence from many studies that PCE values vary with congestion conditions and the amount of trucks in the flow when trucks and autos mix.
|
From page 87... ...
This is an area of research that should be undertaken in the future to improve data inputs and analytical capabilities to accurately estimate the safety benefits of truck-auto separation. A proposed framework to estimate the dependence of accident rates on truck shares and other corridor characteristics (such as grades and number of lanes)
|
From page 88... ...
The postprocessing effort conducted in this study accounted for this deficiency by applying the accident reduction factor recommended by the Douglas handbook to account for the incremental savings in incident-related delay due to accident reduction from truck-auto separation. It is noted, however, that there is a need for improved analytical methods to better understand the true reliability benefits of truck-only lanes.
|
From page 89... ...
His models have not yet incorporated the impacts of delay on access roadways as it affects port and distribution channel choices. It would be possible to build this capability into Leachman's models by conducting simulations of critical access corridors with and without truck lanes in order to establish mean travel times between nodes and standard deviations in these times.
|
From page 90... ...
Typically, urban corridors with significant port truck traffic volumes such as I-710 would have favorable conditions for application of tolls, because a large share of the port truck traffic would be willing to pay tolls to achieve improved travel times and reliability. 90 Separation of Vehicles -- CMV-Only Lanes Source: Adapted from Los Angeles County MTA, 710 Major Corridor Study -- Final Report, March 2005.
|
From page 91... ...
may be relatively small as compared to delays at loading and unloading locations, suggesting that willingness to pay tolls may also be relatively low and potential revenues from tolled truck lanes in urban settings may not generate sufficient revenue to cover much of the cost of the lanes. Staff at SCAG have conducted novel analysis of how taking reliability into account may alter this conclusion.58 The way that truck owners and shippers deal with unreliability is poorly understood, and the affects of travel time reliability benefits of truck-only lanes on willingness to pay tolls is not adequately addressed in most truck-only toll lane studies.
|
From page 92... ...
The key conclusions from the B-C analysis on urban corridors are summarized as follows: • Truck diversion rates of 60% to 70% provide the highest B-C ratios for the truck-only lane alternative. • Very high diversion rates (greater than 80%)
|
From page 93... ...
– 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 corridor for truck shipments.
|
From page 94... ...
Detailed observations could be made of differences in travel times for trucks and autos operating 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.
|
From page 95... ...
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.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.