Table 9. Disposition of May 6, 2014, event comments.
| Topic |
Comments |
Task Lead Response |
| Safety |
| Who are the safety experts you mentioned? How do you contact them? |
Contact information for the DOT multimodal Technical Oversight team is available through the FHWA Office of Freight Management and Operations. |
| How will you address potential bias with fleet data from carriers that are in favor of increases in size and/or weight? This data is not publicly available and therefore not transparent. |
The Crash/Safety analysis area of the Study 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. |
| Does the fleet safety analysis also review short haul fleets and vocational type fleets (garbage, dump, cement haulers) within urban areas? |
Specialized hauling vehicles were not included in the Study. |
| Have you looked at how these combinations operate in States like Michigan, where weights are significantly higher than those combinations that you are studying? |
We did not use data on the configurations that are unique to Michigan. In the Crash and Safety Analysis area, Michigan data was used for 3-S3 analyses in Scenarios 3 and 4. |
| Since weight data is not included in the safety analysis, can you comment on the impact of this data gap to the expected study result? |
The lack of vehicle weight data on crash reports severely inhibited our ability to do an adequate assessment of the alternative configurations with respect to crashes. An axle based assessment using data from a limited number of States was used instead, with the caveat that no national findings could be derived from the analysis. |
| Under Limitations, please explain vehicle weight and its impact on road safety. |
The limitation and its impact is described above in #5. In addition, stopping distance and other kinematic-related operational effects can influence safety. Further, as mass increases, force of impact increases. |
| Would it be possible to secure a list of the names and contact information for the safety experts in order to contact them for future questions? |
Please contact FHWAs Office of Freight Management and Operations for this information. |
| Pavement |
| 23 USC 127 and 23 CFR 658.17 applies to Interstate and defense highways. In addition, the regulation applies to "reasonable access thereto." How do you define the National Network? |
The National Network is defined in Title 23 of the Code of Federal Regulations in Appendix A to Part 658. It was established by the Surface Transportation Assistance Act of 1982 and includes the Interstate System as well as principal arterial highways linking major cities. |
| So I can understand the context applicable to me, into which road category have you placed the Alaska road system? |
Like all other States, Alaskas National Network (AK 1, 2, and 3) is defined in Appendix A to Part 658 in 23 CFR as described above. Alaskas NHS roadways and non-NHS roadways would be handled as defined in their annual highway Performance Monitoring System (HPMS) submission. |
| How do the higher weights, 97,000 lb. affect current road pavement surfaces? |
This information can be found in the findings for the pavement analysis area of the Study. |
| Will pavement impact consider effect of Wide Base Single replacements at minimal, significant and total use for current duals application? |
No, wide-based tires were not assessed as part of the Study; they are not within the scope of the Study. |
| Various fleet weight studies have shown (65 percent to 80 percent) of the fleets bulk out before they reach 80,000 lbs. Will the pavement and bridge phases adopt some (one) of these profiles to facilitate more nearly real world truck weight impacts, and then effect of the various HPVs within the Study? |
The modal shift analysis took into account which truck trips cube out and floor out before reaching the legal weight limit and which trucks reach the weight limit before reaching their cubic capacity. This is an important determination when estimating the shifts from one truck class and operating weight group to another under each scenario. The bridge and pavement analysis took into account the base case or current load distribution situation and compared it to the scenario traffic by truck weight group and truck type. |
| What are the differing impacts onto the roadways from empty trucks and their number of axles? - Does the use of tag or lift axles for reducing tire wear and increasing fuel efficiency when traveling empty have a place in this Study? |
The pavement damage analysis used weigh-in-motion data to estimate the axle weights (and numbers of axles in contact with the road) of empty, partially loaded, and fully loaded vehicles. The Study did not assess tag or lift axles but they were included in the analyses to the extent they were present in the truck weight data used in the Study. |
| Bridge |
| On bridge, consideration of chlorides and non-chlorides does not necessarily imply that both urban and rural bridges are being considered. Chlorides do not discriminate. Also break down of bridge types does not necessarily imply rural and urban: most bridge type can be scaled down or up according to traffic needs. |
Urban and rural were not characteristics used to select bridges from the NBI. Chloride and non-chloride States were groupings used and intended to be used in the modeling of deck deterioration, however, this work was ultimately not performed due to the lack of a generally accepted deck deterioration model. |
| Not develop new forecasts of future travel levels because you assume it is increasing? Isn't it worth measuring how different configurations can influence the rate of increase? |
FHWA determined that the use of truck travel forecasts and forecasts for the expected increase in freight demand over time would make it hard to isolate and identify the potential impacts to modal shift and other areas of analysis of different truck configurations compared to those under current Federal truck size and weight limits. For that reason, freight growth was artificially held constant in the Study. |
| How can the current bridges handle the 97,000 lb when they are all failing? |
The Study team analyzed the effects of the alternative configurations on each of the 490 representative bridges and provided immediate structural impacts and the longer term accrued damage costs, which can be found in the bridge analysis technical report. The "normalized" Rating Factors attributable to each Scenario were tabulated and compared in terms of bridge type, age of bridge, and span length. |
| Your slide mentioned "reasonable access" to Interstates. It is important to distinguish between the concept of "reasonable access" under a Federal mandate such as the current 80,000 single axle weight limit as opposed to a State option approach that would allow states to allow interstate access to heavier, six-axle trucks. There is no need for reasonable access requirements under the State option approach since States will continue to control weight limits on non-Interstate roads. |
The Study did not assess a State option approach; it was not considered in the scope of the Study. |
| It is a common misconception that current US bridges are ALL failing. Many, many bridges now considered structurally deficient can safely handle increased weights, especially those on the NHS, and in particular, if they have structural monitoring systems installed. |
Comment noted; no response required. |
| Could you please confirm that the cost of each of the proposed trucks will be A+B+C+D+E (i.e., your 5 subtasks)? |
The bridge analysis technical report identifies one-time costs resulting from the need to strengthen or replace bridges as a result of introducing certain alternative configurations. As explained in the Volume I Summary report, costs across the Study analysis areas are not additive, and the one-time structural costs represent an extreme upper bound. |
| How can you map subjective NBI data on bridges to actual damage resulting from overweight trucks vs. inadequate maintenance, for example? Seems like a stretch to me. Perhaps the bridge study should have a serious disclaimer. |
We used the NBI data to screen the 490 bridges to be structurally analyzed such that they are representative of the national inventory of bridges for each region and highway network, by bridge type, span length, and age. |
| What is the range of span lengths that will be included in the bridge study? |
The span lengths for all bridges listed on the NBI were used. The length intervals can be found in Table 6 of the bridge analysis technical report. |
| What percentage of repair costs is being attributed to loads? |
Intended analysis on accrued bridge damage costs was not completed due to the lack of a generally accepted modelling method and approach. |
| Do you have any preliminary results from the bridge analysis to share? |
Results were not available at the time the request was made (May, 2014) but all information developed as part of the bridge analysis area of the Study is available in the technical report that was made publicly available on June 5, 2015. |
| On one of the slides it stated that 500 representative bridges would be used in the Study and only LRFR rated bridges would be evaluated. Since FHWA only required LRFR ratings on bridges that have been built in the last 10 years or so, will you in effect only use new bridges with a higher than average load capacity be evaluated? |
No, the bridges that were analyzed were screened to ensure they were representative of the NBI in terms of age and design standards. |
| Can you please clarify how a comparative study of rating factors for the different loads might translate into damage and repair costs? |
These two issues are pursued on separate paths for the purposes of this Study. The comparison of rating factors was employed to identify those bridges that have posting issues or that would face an immediate structural risk in response to the alternative truck configurations, and then to derive and tabulate the corresponding costs to strengthen or replace those bridges. The analysis of accrued damage costs that was attempted but not completed was designed to use a separate axle load based allocation of bridge damage costs by vehicle (truck) class. |
| How can the calculation of rating factors based on strength capture deterioration (i.e., a service limit State phenomena)? |
They are separate analyses. See the response to question 12, above. |
| Rating factors are based on a strength-level analysis. If a cost is not being calculated for fatigue and deck subtasks, how will deterioration (i.e., a service limit State phenomenon) be captured cost-wise? Will the bridge cost estimate be based on the sum of three of the subtasks? |
Please see the response to questions 6 and 12 above. |
| Glad to hear that the percentage of load-related bridge costs is still being worked on. |
Comment noted; no response required. |
| Enforcement/Compliance |
| As most heavy vehicles (Class 8) on the road do not know, at the point of loading, how much they carry and how their loads are distributed across the axles, will there be a requirement for trucks to carry on-board scales for management of truck weight and load weight? |
The Technical reports did not make recommendations regarding introducing new technologies or systems on trucks. |
| Modal Shift |
| Will there be any analysis done on the environmental impact of increasing weight limits (i.e., heavier loads = less trips = less fossil fuels being used)? |
The impacts of truck size and weight scenarios on fuel consumption and carbon dioxide and nitrogen oxide emissions were assessed in the modal shift analysis area of the Study. Findings from the work completed in that area of the Study are found in the technical report including impacts from changes in VMT and changes in fuel consumption and emissions rates for each of the alternative configurations included in the Study. |
| How will this Study factor in any environmental improvements from reduced carbon emissions that result from fewer trips? Interested in the correlation between weight/trips/carbon footprint. |
Emission rates for the scenario vehicles were estimated based on their estimated operating weight distributions and the increased engine size they are assumed to require. Emissions rates for scenario and base case vehicles are applied to base case and scenario VMT to estimate impacts of each scenario on CO2 and NOx emissions. |
| Have you decided to incorporate the possibility of a competitive response by the railroads in your analysis of intermodal shift? In other words, if the railroads lower their rates to keep business, this will be a factor in any shift of freight from rail to truck. Are you considering this? |
Yes, railroads were assumed to lower rates if necessary to retain existing traffic. Rates could not be lowered below variable costs, however. The Study also estimated impacts of changes in rail rates on the contribution of traffic to meeting rail fixed costs. |
| Where does operating cost/efficiency based on truck size/weight enter the diversion analysis? |
In general, operating costs per mile are combined with non-transportation logistics costs to estimate total costs for base case and scenario vehicles to transport different commodities between various origins and destinations. The alternative with the lower total transportation and logistics costs was assumed to be chosen. |
| Does DOT have Drag and Rolling Resistance data compatible with the EPA-Truck GHG Rule or the HPVs being considered in the Study? |
The fuel consumption model used for this Study includes drag and rolling resistance factors compatible with EPAs GEM model. |
| Has there been any analysis or consideration given to intermodal/transloading type jobs due to trucks being able to carry larger loads? |
Estimating potential impacts of truck size and weight scenarios on employment is not within the scope of this Study. |
| Will the Study consider the private sector pavement in other services? Garages, dealers, truck stops? |
No, estimating impacts on paved surfaces at private sector facilities that serve scenario vehicles was not within the scope of this Study. |
| When considering cost to the industry would you not consider the cost of purchasing new equipment required to meet new standards? |
Detailed cost estimates for different segments of the trucking industry to shift to new equipment are not within the scope of this Study. The differential cost of operating scenario equipment compared to base case vehicles was considered in estimating the extent to which shifts would occur, however. |
| Can you work through a hypothetical case? For example, if cost per Gross Ton Miles for a larger truck were 20 percent lower than the base case, how would you determine the public cost impact of achieving that operating saving? |
Each commodity type was assumed to be hauled in one or more body types that have different operating costs per mile and to have different payload distributions all vehicles do not operate fully loaded all the time. For those shipments that could benefit from the higher weights allowed on the scenario vehicles, operating costs were combined with inventory carrying costs and other non-transport logistics costs to estimate the total costs of using the scenario vehicle compared to base case vehicles for shipments between all origins and destinations between which each commodity is transported. The alternative with the lower costs was assumed to be selected. Potential modal shifts were estimated for all commodities traveling between all origins and destinations. Based on this analysis, changes in VMT and operating weights for base case and scenario vehicles were estimated for each highway functional class. These changes in VMT and operating weights were used to estimate changes in pavement and bridge costs, crashes, enforcement costs, transportation and logistics costs, railroad impacts, fuel consumption, and CO2 and NOx emissions. Quantitative impacts were estimated for each of these areas, but only the pavement and bridge costs, transportation and logistics costs, and rail impacts were estimated in monetary terms. |
| CFR = Code of Federal Regulations CO2 = Carbon dioxide DOT = U.S. Department of Transportation EPA = Environmental Protection Agency FHWA = Federal Highway Administration GHG = greenhouse gas HPMS = Highway Performance Monitoring System LRFR = load & resistance factor rating NBI = National Bridge Inventory NHS = National Highway System NOx = nitrogen oxide USC = U. S. Code VMT = vehicle miles traveled |
