Table 8. Disposition of December 18, 2013, event comments.
| Topic |
Comments |
Task Lead Response |
| General Comments |
| Why is there such a short timeline to submit comments? |
FHWA invited and considered comments from May 2013, prior to the launch of the Desk Scans and selection of alternative configurations, data sets, models and methodologies, throughout the research phase of the Study and following the June 2015 release of the Technical Reports and September 2015 Peer Review. A public docket for submitting and sharing comments was created in the fall of 2014, populated with previously submitted comments, and will remain open for a period of time following the release of the final Report to Congress. |
| Modal Shift |
| Is the Study going to look into the effects of having longer combinations on surface streets and if not, are they going to take into account the need for more drop lots or perhaps warehouses to build up or break down the loads as they come in and out and off the Interstate? |
The modeled twin 33 ft. trailers were assumed to have the same access as the baseline twin 28 ft. trailers. No assumption was made regarding infrastructure to accommodate twin 33s. Triples were assumed to be limited to a 74,500 mile network of Interstate and other principal arterial highways, with additional access of up to a maximum of 2 miles from that network. It was assumed that no public infrastructure would be provided for triples to assemble or disassemble. |
| What kind of impacts are you looking at for the railroads? Economic, modal shift? |
The study estimated the potential shifts of traffic from railroads to highways, potential reductions in rates that would be needed to retain certain traffic on railroads, and the loss of contribution toward meeting railroads’ fixed costs. |
| What steps will the Study take to examine shift within trucking itself? There is a significant amount of the trucking industry – specifically small business trucking entrepreneurs – that will be negatively impacted by changes in limits, yet the examination of impacts on shipments seems to only be focused on benefits to shippers. |
The Study examined impacts of scenario vehicles on truckload and less-than-truckload operations. The modal shift analysis included an assessment of truck-to-truck shifts that would occur through introduction of each of the alternative configurations. The Study did not differentiate impacts on specific segments of the trucking industry such as small business trucking entrepreneurs. |
| Do you have further documentation on county-to-county commodity flows? If so, please direct. |
County-to-county flows were developed by Oak Ridge National Laboratory based on FHWA’s latest Freight Analysis Framework (FAF). Origins and destinations at the county level were estimated from regional flows in the FAF based on Bureau of Economic Analysis and other economic data. Documentation on the steps involved in preparing the county-to-county freight flows is included in the modal shift analysis final technical report. |
| Will the modal shift analysis examine railroad and Surface Transportation Board (STB) policies with regard to intermodal and intermodal competition, bottleneck rates, paper barriers, interchange, terminal access, shuttle and unit train operations, and the lack of rail service in parts of the United States? |
The modal shift analysis looked at potential modal shifts based on current policies, industry practices, and existing railroad services in different parts of the country. Waybill data limit the types of rail operations that can be analyzed. An assessment of STB policies is outside the scope of this Study. |
| Whether traffic shifts or not is not just a factor of costs but also profit margins. In many cases, traffic will not shift if the non-trucking mode opts to lower shipping rates to retain the traffic. How will that be taken into account? |
Rates reflect different market conditions between origins and destinations. In the case of railroad rates, it was assumed that railroads would lower rates, if necessary, to retain traffic, but their variable cost represents a floor below which they would not lower costs. |
| How are you incorporating the differences between the States with regard to their acceptance of each scenario? Some States still do not allow triples and the mods will depend on the current load rating/capacity allowed by each State or even by existing facilities. |
For purposes of the Study, it is assumed that States would be required to comply with the scenario size and weight limits, much as they were required to allow twin trailers pursuant to the STAA of 1982. No State-by-State adoption assumptions were applied in the Study. |
| How much added expenses do you expect will be shifted to city budgets and truck stop operators? Does this shift expenses from carriers to the public for higher carrier profits? |
The Study did not attempt to break out costs that might be incurred by local governments or truck stop operators. The Study noted that some pavement and bridge costs associated with the various scenarios are traditionally borne by local governments (a fact highlighted in many public comments to the Study), but no assumptions were made regarding who would pay for any added infrastructure costs. |
| With the ITIC model, how were the non-transportation costs developed and what is the data source? |
FHWA has maintained and updated the theoretical and data underpinnings of the ITIC model since its first use in the 2000 CTSW study. The non-transportation cost estimation procedure of the model was updated by the Pennsylvania State University during the 2004 Western Uniformity Study and a subsequent 2006 study. The interest rate for inventory carrying cost was updated using Moody’s investment grade bond yield for 2011 plus 1 percent; truck rates were updated using Producer Price Indexes for general freight trucking. |
| Are you going to consider the unintended environmental impacts when road freight movement is shifted to heavier vehicles? The new concept of environmental life-cycle assessment as significant emissions result outside the operational phase. The majority of emissions of PM10, SO2 and Pb will be increased as infrastructure will have to be repaired more often and those maintenance cost and emissions are much higher during repair processes. |
No, environmental impacts associated with construction and maintenance activities were not estimated. Qualitative assessments on this subject are included in the Study. |
| Will the modal shift analysis include road transport to/from the remote locations such as grain elevators that are the overwhelming source of the majority of commodity movement in most counties (Estimated at over 80 percent of counties in Illinois) and has the Agriculture Industry been invited to provide input into this process accordingly? |
Local moves including shipments of cereal grains and other agricultural products identified in the FAF are included in the modal shift analysis area of the Study. All stakeholders were invited to share their input to the Study. |
| Will the Study include a review/impact of time spent or delay due to check weighs or rework at each dock or terminal? (Before the vehicle actually hits the highway?) |
The non-transport logistics cost calculation includes terminal/dock wait time – the time for each additional trailer is an additional 50 percent of the single trailer time. The analysis of compliance costs included an analysis of the additional time to weigh scenario vehicles for weight enforcement purposes. |
| The modal shift analysis did not appear to take into account shifts or displacement within the trucking industry. Increased use of larger, heavier trucks, and most specifically longer combination vehicles such as double and triple trailer combinations, will disadvantage the vast majority of motor carriers that are small businesses and exclusively operate truck semitrailer combinations. This may also coerce smaller operators who currently run legally to illegally overload their vehicles in order to remain competitive. |
Truck-to-truck shifts generated through introduction of the scenario vehicles were included in the modal shift analysis area of the Study. The analysis did not explicitly attempt to quantify impacts on small trucking firms. Potential impacts were presented in general terms. |
| Will additional loading and unloading time and hook-up and break down time be considered as an expense for the drivers because of reduced mileage? |
The added time required to handle multi-trailer combinations is included in non-transportation logistics costs, but such costs were not assigned to different segments of the freight transportation industry – shippers, carriers, drivers, etc. |
| How will this impact driver pay, do you expect drivers to get additional pay for the increased responsibility for the size of the proposed loads? |
Potential impacts on driver pay were not explicitly considered in the Study, although the freight rates for multi-trailer combinations used in the modal shift analysis are higher than for single trailer configurations, reflecting higher equipment costs and driver wages for the multi-trailer combinations. |
| The United Kingdom (UK) uses heavier six axle trucks and during the review of their implementation they saw more freight tonnage shipped on fewer vehicle miles. Would this real world example not be of use to the Study? |
Studies from the UK were included in the Desk Scan phase of the Study. While findings from such studies are useful, freight transportation characteristics in the U.S. differ from those in other countries and it was important to reflect potential impacts in the U.S. |
| Will the customers not make most modal shift decisions based on the best value to them? |
A national study such as this cannot reflect all factors that enter into individual mode choice decisions, but the Study attempted to consider major factors that generally affect mode choice decisions. |
| Can you provide a list of the assumptions to be used in the ITIC model, and how they differ from those used in the 2000 CTSW Study, especially those that relate to rail diversion? |
A complete list of assumptions used in the ITIC modal shift model was included in Appendix C of the modal shift technical report. Scenarios being analyzed in the current study were different from those analyzed in the 2000 CTSW Study and, as such, different assumptions were applied. |
| How will the modal changes impact different parts of the country? For instance, where there are large steel industries, how will modal impacts happen in Michigan (with very heavy trucks) versus Alabama, where there is a lot of steel, but low weights? |
The analysis did not explicitly estimate differential impacts on modal diversion at the State level, however, the FAF data set and truck weight data used in the Study account to some extent for the situations referenced in this comment. |
| Any comments as to widened Panama Canal impacts on east/west coast freight? |
The Study analyzed 2011 freight flows and is not explicitly attempting to estimate how future changes to the global freight transportation network might be impacted as a result of Panama Canal widening or other external factors. |
| Safety |
| Will you be doing a study on crush and kinematic dynamics on heavier trucks as the crush factor on both the truck and whatever the truck hits (passenger cars) will exponentially increase hence more fatalities? Also, Commercial Motor Vehicle cab requirements-- are they suitable for accidents with heavier weightings? |
We did not explicitly consider crush and vehicle kinematics. We assessed changes in severity of crash outcome. |
| With heavier trucks, there will be more of a roller coaster approach to hills. If speed is regulated downhill, how much more danger will the public be in from slow moving vehicles and will additional enforcement be needed as a result? |
The operational impacts of alternative configurations on the traffic stream were assessed as part of the modal shift area of the Study. |
| Should there be discussions to develop additional training for Commercial Drivers License (CDL) requirements to include a size and weight endorsement? |
This is not within the scope of the Study. |
| Is the technical data FHWA is collecting about safety performance based upon real-world experience, or is it simply information provided by manufacturers during test-track operations? |
Technical data used in the crash/safety analysis area of the Study included crash analysis, inspection and violations analysis based on real-world experience. No manufacturers’ test track data was used in the Study. |
| Has any research been done on the effect of triples operating in congested eastern States taking into account the safety concerns of the aging population increasing? |
Since the safety analysis used actual crash information, collected from the areas in which these vehicles operate, it was not possible to study the effect of triples in congested eastern States of the U.S. |
| Will the highway safety/truck crash analysis account for the less accommodating geometrics of the Local Road system, including those areas of reasonable access? |
The vehicle stability and control assessments conducted as part of the crash/safety analysis apply to those roadway systems; they are not specifically tied to the geometrics of Interstate or NHS roadways. |
| The stopping distance data on the various configurations would seem to be directly on point with the information needed by Congress. Will DOT commit to including it in your analysis? |
Findings from these FHWA/FMCSA braking distance tests were included in the Crash/Safety analysis area of the Study. |
| Will this analysis include winter driving conditions and load securement requirements for heavier loads? |
The crash data examined included winter operations. An assessment of load securement was not conducted; it is outside the scope of the Study. |
| In considering experiences in other countries, will FHWA be addressing the differences in driver training requirements between the United States (zero requirements) and foreign countries (high training requirements in Europe, for example)? |
Information from studies conducted in other countries was evaluated for relevance in the Desk Scan phase of the Study, with critical differences identified. In this case, an assessment of driver training requirements in the US compared to other countries was not included in the Crash/Safety analysis; this is outside the scope of the Study. |
| For fleet-based method, what steps will be taken to address potential bias with organizations and carriers providing fleet data that are also proponents of increases in truck size and weight? |
An approach was designed to utilize information from three disparate sources (corridor-based, State data-based and fleet data-based) to control for any bias. Ultimately, fleet data was not used in the Study, rendering moot any concern over bias from commercial data sets. |
| In the safety analysis Model Vehicle simulation, will tractor roll stability control and yaw stability control along with trailer roll stability control be considered in the performance measures evaluation? |
Electronic stability control on the tractor or trailer was not included in the Study because NHTSA was pursuing rulemaking on electronic stability control as the Study was being conducted. |
| Will the stopping distance analysis account for the current State of vehicle maintenance and overloading of vehicles as identified by roadside violation data? Will the analysis account for the less-than-ideal stopping distances for that portion of the vehicle fleet consistently found to have brake / tire / overloading issues? Will the analysis include an estimated impact upon safety in these areas when examining the proposed configurations? |
Two of the scenarios that were simulated in the vehicle stability and control analysis included braking and were run using proper brakes and various brake failure conditions. |
| What will you be doing to look at real world experiences? Are you talking to truckers who operate these vehicles? |
Where possible, the Study methodology incorporated data from real world conditions. Truckers were not interviewed as part of the Study, however, trucking organizations submitted comments during the course of the Study and those comments were given consideration. |
| How will the analysis account for the differences in operating conditions between the States involved in the Study and the expected operation and safety performance on roads nationwide? |
Methods to extrapolate findings to the national scale are described in the relevant areas of the Crash/Safety analysis. It should be noted, however, that crash analysis findings could not be extended to a national level due to data limitations. |
| While conducting the safety analysis, will you be studying actual trucks and truck crashes in a controlled environment? |
The crash analysis conducted in the Study did not include truck crash testing in a controlled environment. Vehicle stability and control tests were simulation-based. |
| How will you address crash severity with heavier trucks causing greater damage? |
Comparisons of crash severity for baseline and candidate configurations were included in the Crash/Safety analysis area of the Study. Findings on crash severity differences for each of the alternative configurations are presented in the Study. |
| Current LCV operations use drivers with above-average experience, more training and higher pay. How will these factors be taken into account in studying matched pairs? |
The matched pairs technique originally proposed for use in the Study was not feasible due to data limitations; driver attributes were assessed as part of the violation and citation area of the Crash/Safety analysis area of the Study. |
| Are you meeting with State Troopers or other first responders who are the usually the first people on the scene of a truck crash? |
Enforcement personnel at CVSA contributed expert input to various areas of the Study. No outreach was conducted with first responders in the crash analysis area of the Study. |
| As you are utilizing WIM data to determine results in your Study, how will you differentiate the information as there is no identifier as to what type of load was on the vehicle (reducible vs non-reducible)? |
WIM data was used extensively across all areas of the Study. The aspect that a load might be divisible is not relevant to the analysis completed in the Study |
| With increased size and weight, will there be any mandatory cab safety standards established to better protect the driver of the truck to increase probability of survival of a crash? |
Developing new cab safety standards is outside the scope of the Study. The Study sought to address the potential impacts of changes in truck types. |
| Will the analysis of crashes include property crashes off the Interstate System as LCVs off tracking can cause curb damage, signs knocked down and crashes from turning into local roads? |
The vehicle stability and control assessment included in the Crash/Safety analysis area of the Study addresses and presents findings relevant to tracking issues. |
| Will the CTSWL Study examine increased wear and tear on truck safety equipment, including brakes? |
Within the limits of the data available to conduct such assessments, equipment-related violations (e.g., brake related) were compared between the alternative configurations and the control vehicle. In addition, differential effects of brake failure were studied in the vehicle stability and control assessment area of the Crash/Safety analysis. |
| Will engine horsepower be considered as a factor in holding back a load and pulling a hill faster? |
Yes, the operational performance of each of the alternative configurations was assessed in the modal shift analysis area of the Study using various terrain settings. Horsepower and fuel consumption were included as part of the assessment. |
| I was wondering if there were any studies done, or if it will be done in the Study as to whether the longer heavier combinations will increase the death rate among accidents? A few weeks ago it was mentioned at the HOS [Hours of Service] hearings by FMCSA that if the new HOS saves one life it is worth putting in. As longer combination vehicles increases the death rate then I do not feel that they should be allowed. |
Differences in the distribution of crashes by severity type were assessed as part of the Crash/Safety analysis area of the Study. |
| I just wanted to hit on something that did not seem to be addressed at all and that is railroad track crossings. One, they are going to wear more quickly and number two, it is going to take a longer time to stop and be prepared for that. How are you addressing that? |
To the extent that grade crossing crashes were included in the data sets used in the Crash/Safety analysis area, they were included in the Study. Findings from the assessment of changes in stopping distances associated with each of the alternative configurations was included in the vehicle stability and control assessment in the Crash/Safety analysis area of the Study. |
| My second part is, actually what is most important to me as the mother of someone who was killed in a truck crash, why is the crash data potentially inclusive? Why is it not one of the top considerations in truck size and weight increase? |
DOT holds transportation safety as its highest priority. The Crash/Safety assessments were included in the Study along with other aspects of assessment in order to present a comprehensive picture of the impacts that a change in current Federal truck size and weight limits would have. Areas of the Study requiring assessment were outlined in MAP-21. |
| I am wondering, are we going to be considering the Maine and Vermont pilot program study results when we talk about the infrastructure and bridge damage and safety concerns that was also noted in the 6-month evaluation? |
The Desk Scan phase of the Study included the Maine and Vermont studies. Methods, data and models from those studies were considered similar to the other prior studies that were included in the Desk Scan phase. |
| I have a question, has the agency considered the effects of longer and heavier vehicles such as triples accelerating from a standing stop to get through a highway railroad grade crossing? The reason I ask is, the current rules require 20 second warning before a train arrives at that crossing and also, the trucking regulations require trucks to stop before a grade crossing until there is sufficient room on the other side to clear the vehicle. With those factors in play, I wondered if the agency had considered LCVs accelerating from a standing stop at railroad grades? |
The operation of LCVs at rail crossings was not a specific area of analysis in the Study. The operational performance of LCVs are assessed in the modal shift analysis area of the Study. |
| Pavement Comparative Assessment |
| Will the pavement comparative assessment account for lesser pavement types prevalent on the local road system, including those areas of reasonable access included in the modal shift component, that generally consist of a thin layer of aggregate upon compacted native earth with a sealcoat surface? |
This area of assessment was only addressed in a qualitative manner due to a lack of data on local roadways. |
| Will the pavement wear consider the differences between two axle and multiaxle wear due to scrubbing and in different temperature zones as well as pavement types? |
The pavement structural responses to two axles and multi-axle set configurations were assessed with regard to pavement impacts for the four different climatic regions in the United States. Findings of these assessments are found in the pavement analysis area of the Study. |
| Do the models that FHWA will be using allow for this testing related to tire scuffing in intersections and other areas where trucks will be turning? If not, what steps will the Study be taking to examine these issues? |
No, the AASHTOWare® Pavement ME Design software does not provide the capability to conduct such assessments. |
| Is your pavement-wear evaluation based on (1) deterioration per vehicle, (2) per tire, or (3) per unit of cargo shipped? |
The assessments completed in the pavement analysis area of the Study produced results attributed to the scenario traffic associated with each of the alternative configurations. Results were reported using measures of change in pavement service interval and life-cycle cost. |
| Are you considering the impacts of technologies like weight equalization across trailer axle groupings and self-steer axles? |
The research did not include assessments of advanced technologies; they were not in the scope of the Study. |
| Is there a list of what LTPP test sections will be used for each of the four pavement category studies? |
Yes, this information is presented in the appendices to the pavement analysis area of the Study. |
| Does the pavement analysis group believe that the completeness of this portion of the CTSWL Study is limited by the congressionally mandated timeline? |
The time schedule for completing the Study did not adversely affect the robustness of the analysis performed with regard to pavement impacts. |
| The use of wide base tires is on the rise, when will it be considered on this Study or just the FHWA pooled fund study? |
The evaluation of wide-based-tires was not in the scope of this Study. Further, the AASHTOWare® Pavement ME Design software does not possess the capability of conducting such assessments. |
| Will the Study consider the different stages of pavement life where the axle weights will affect the pavement differently? |
Yes, the AASHTOWare® Pavement ME Design software consisted of incremental accumulated damage models for all of the pavements’ structural distresses. It also has aging models built in for flexible pavements and strength gain models built in for concrete pavements. The software also considers changes in unbound layers over time as well as daily, monthly, and seasonally. |
| Will your data modeling be updated to include information not currently available? |
Recommendations for improvement in models or data availability were reviewed as they were submitted, and considered to the extent possible given the status of the Study. Additional recommendations resulted from the NAS Peer Review panel. There is no current program or plan to modify the technical work of the Study; however, data sets (such as FAF) that were used for the Study may follow their own update cycle. |
| Given the State option nature of the six-axle proposal, it is good that you are reviewing certain networks and not all roads. States that do not allow the heavier configurations on their Interstates certainly won’t be allowing them on local roads. |
Comment received; no response required. |
| First above regarding the pavement and infrastructure, are these studies assuming pristine infrastructure conditions at the onset or are the actual current of the structure conditions being used in any or all of the analysis? |
The pavement analysis that was completed used the AASHTOWare® Pavement ME Design software. Due to the limitations of the currently available software, all analyses were for newly constructed pavements. |
| Enforcement and Compliance Assessment |
| Many States utilize the Federal bridge formula to enforce weight regulations. Will you come out with a new Federal bridge formula if the weights will be raised? |
Changes to the bridge formula are outside the scope of the Study. A list of current Federal laws that would be affected by any changes to allowable truck weights are identified in the compliance analysis area of the Study. |
| Will the enforcement and compliance assessment account for traffic to, from, and upon the local road system, including those areas of reasonable access? |
These impacts may be reflected in the self-reporting to FHWA by some States as part of annual certification of truck size and weight activities and state enforcement plans. |
| Estimates for, and the effects of, compliance (or rather non-compliance) under any truck size and weight alternative studied as part of the Study must be included. |
3. Impacts on the delivery of effective truck size and weight enforcement programs were assessed in the compliance analysis area of the Study. |
| Will you be looking at the lack of fixed scales facilities nationwide, and/or collecting data State by State on the number of fixed and portable scales per State? |
Weighing equipment is included in data submitted to FHWA by the States in their State Enforcement Plans and Annual Certifications. This data was included in the compliance analysis area of the Study to the extent it was relevant to the work that was completed. |
| Will inspection facilities need to be upgraded to fit longer vehicles for level 1 inspections? Will multiple vehicle combinations be inspected at the same rate as regular truck trailer combinations? |
Expert opinion was provided by CVSA on whether changes to truck enforcement facilities, such as weigh-bridges, would be necessary if alternative configurations were allowed. The compliance analysis includes input on how LCVs are weighed and how the practice might need to be altered to reflect changes in vehicle types, however, no corresponding change was anticipated for inspection equipment. |
| What is the role and composition of the CVSA (Commercial Vehicle Safety Alliance)? |
From the CVSA.org Web site: CVSA is an international not-for-profit organization comprised of local, state, provincial, territorial and federal motor carrier safety officials and industry representatives from the United States, Canada, and Mexico. CVSA’s mission is to promote commercial motor vehicle safety and security by providing leadership to enforcement, industry and policy makers. |
| Will the Study consider the increased restrictions expected to be caused by increased weight postings of bridges analyzed for specialized hauling vehicles (SHV)? |
An assessment of specialized hauling equipment was not within the scope of this Study. |
| Can trucks with on-board scales assist with data accumulation for compliance? |
This source of truck weight data was not made available for the CTSWL Study. |
| In the phrase - “method to link overweight trucking and safety” - Do you define “overweight truck” as a vehicle in violation of current law or any of the configurations proposed for evaluation in the Study? Do we have an apples v. oranges problem? |
The language in §32801 of MAP-21 required that legally operating over-weight trucks (those with a State issued permit) and illegally operating over-weight trucks be treated the same for the purposes of this Study. |
| Will you look at the impacts on enforcement cost and effectiveness due to heavier trucks shifting from non-Interstate to Interstate highways? |
The scenario traffic used in the compliance analysis captured such shifts. Furthermore, enforcement effectiveness and cost metrics were reported in the compliance analysis of the Study. |
| The 2009 WIM data from FHWA showed that the average single trailered combination weighed 54,000 pounds while the average multiple trailered rig weighed 59,000 pounds. Does that still sound about right? |
Average truck weight was not reported in this Study, however, this information is available from the Traffic Monitoring staff in the FHWA Office of Highway Policy Information, who participated in the Study. |
| Will performance measures be identified for enforcement and compliance programs? |
These are included in the compliance analysis technical report. |
| Will the Study look at the problems that LCVs will have on truck parking especially in rest areas and the fact that LCVs require pull through parking for the most part? |
A qualitative discussion on this topic was included in the Study but no assessment was completed due to the lack of available data. |
| Bridge Comparative Assessment |
| Will the bridge analysis report mention the availability of simple, commercial, cost-effective monitoring tools bridge owners can use to provide early warning of overload damage, e.g. strain sensors, instead of continued reliance on subjective, biennial visual condition assessments which cannot detect onset of fatigue damage or accurately assess progression of other failure mechanisms, such as cracking? |
No, the Study did not assess benefits of bridge monitoring technologies; this is not within the Study’s scope. |
| How will bridge substructures be included in the models? |
The analysis and findings of fatigue included in the bridge analysis area of the Study included an assessment of superstructure impacts. |
| Thank you for including impact caused by additional posted bridges. Will you study impact on increased costs to infrastructure, pavement, trucking industry due to increased number of miles traveled as result of new bridge postings? |
The issue of detours created by bridge postings was qualitatively addressed in the Study. Each bridge posted would be associated with its own detour; thus, consideration of such detours would be too site-specific for extrapolation to a national study. |
| What method will be used to select the bridges to be used in the model analysis? |
We screened all of the approximately 143,000 bridges on the Interstate System and NHS included in FHWA’s NBI and characterized them by bridge type, primary structural material, span length, year built, etc. We then procured 490 completed bridge analysis models (VIRTIS models) representative of the proportion of all similar bridges on the NHS. |
| Four conventional trucks compare to 3 high-productivity trucks: will the Study present bridge wear estimates relative to this type of modal shift? |
No; each of the alternative configurations were modeled through the modal shift analysis step and produced scenario traffic. Scenario traffic was compared to current traffic to develop findings on the impacts of introducing each of the alternative configurations. |
| Will the bridge comparative assessment account for both NBI and non-NBI structures? |
No, non-highway bridges and bridges not listed on the NBI were not included in the Study. |
| Will the structure assessment methodology be able to predict the reduced life cycle of the structure, and how that affects agency asset management decisions? |
Life-cycle-cost techniques were not applied in the bridge analysis area of the Study. With the lack of a generally accepted bridge deck deterioration model, LCC for bridges could not be accomplished. |
| In States that already allow six axle trucks, allowing Interstate access will shorten some truck routes and take pressure off local bridges. Will the Study account for this? |
In this national Study, we assessed the impacts of each alternative configuration, including total truck travel demand. Specific truck travel changes on specific roadway networks were not assessed in the Study. |
| At the TRB meeting the number of bridges being used as a sample was stated as 500, the current presentation indicates about 400. Does this represent a change and does about 400 mean that it could be less than 400? |
There are 490 samples used in the Bridge Analysis. Based on the characteristics of the Interstate System and NHS bridges listed on the NBI, the 490 bridges selected were representative of the population included in the analysis. |
| Would additional assessment need to be performed using expensive live load testing to determine actual impact and potential need for strengthening or replacement before the heavier loads are permitted? |
No, but load rating analysis may be necessary for specific bridges. |
| How is the standardized axle method for bridge damage a different metric than the ESAL method for pavement damage? Would it be better to have consistent methods to estimate damage to bridges and pavements? |
Neither was used. We used actual recorded axle weights. The pavement analysis area of the Study did not use Equivalent Single Axle Loads units; actual measured axle loadings were used to develop the load spectra required as input to the AASHTOWare® Pavement ME Design software. |
| How many different Bridge designs were included in the 400 bridges and did you consider age of these bridges as a factor? |
We did use the age of bridge as characteristic when constructing the sample framework. Bridges built between 1910 and 2004 were included. We included the eleven most common bridge types, representative of more than 96 percent of all bridges. |
| With many States allowing gross vehicle weights over 95,000 pounds on five axle rigs, will the Study account for the fact that many of these loads will shift to six axle rigs with lighter axle loads? |
The truck weight data set used in the Study includes actual vehicle weight measurements reported to FHWA by the States. The situation described would be included in that data set. Shifts from truck-to-truck were modeled in the modal shift analysis area of the Study. To the extent it is in the WIM data used in the Study and the truck-to-truck modal shift analysis that was completed, such shifts were accounted for in the Study. |
| We have trucks running well over 80,000 for over 25 years in nine Western States with different caps like 95,000 in Nebraska, 117,000 in Wyoming, 129,000 in the Dakotas, Nevada, and Utah. We have been doing this for years and years with the Interstate and secondary alike. Formula B since 1975 it has been used universally throughout the nation except maybe Michigan. There are thousands of pieces of equipment that are running now under formula B so it seems to me, if you just extend bridge formula B beyond the 80,000 pounds, we have already got history, proven specs and this would really be better for the economy and everybody would be on the same playing field and would have less pounds per square inch on their pavement if we would just use of federal formula B over 80,000 pounds. |
Comment noted; no response required. |
| With all due respect, your last commenter the Western States have been running have your trucks for years and years, I agree but their highways and bridges were also built to withstand those heavier trucks. I live in Pennsylvania and Pennsylvania currently leads the Nation with 4479 structurally deficient bridges. We are 27th in the Nation with structurally deficient bridges that are posted for weight limit or closed and the average bridge age in Pennsylvania is 51 years old. We just recently went through in the last 4 or 5 months having 1000 new bridges added to that list and posted low weight limits. Pennsylvania is also one of the highest States in the Nation for truck miles traveled because of its geographic location leading into the east and northeast. I really do not think our roads and bridges in Pennsylvania can withstand that many more heavier combination vehicles traveling on the roadways without having them completely deteriorate with a going to be absolutely undrivable. |
Comment noted; no response required. |
| CDL = commercial drivers license • CTSW = 2000 Comprehensive Truck Size and Weight Study • CTSWL = comprehensive truck size and weight limits • CVSA = Commercial Vehicle Safety Alliance • DOT = U.S. Department of Transportation • FAF = Freight Analysis Framework • FHWA = Highway Administration • FMCSA = Federal Motor Carrier Safety Administration • HOS = Hours of Service • ITIC = Intermodal Transportation and Inventory Costing • LCV = Longer Combination Vehicle • LTPP = Long-Term Pavement Performance program • MAP 21 = Moving Ahead for Progress in the 21st Century Act • NAS = National Academy of Sciences • NBI = National Bridge Inventory • NHS = National Highway System • NHTSA = National Highway Traffic Safety Administration • Pb = Lead • PM10 = Particulate Matter of 10 Microns in diameter or smaller • SHV = specialized hauling vehicles • SO2 = Sulfur Dioxide • STAA = Surface Transportation Assistance Act of 1982 • STB = Surface Transportation Board • UK = United Kingdom • WIM = Weigh-in-Motion |
