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Comprehensive Truck Size and Weight Limits Study - Bridge Structure Comparative Analysis Technical Report

Chapter 4: Scenario Cost Summaries

As noted in Volume I: Comprehensive Truck Size and Weight Limits Study – Technical Summary Report as well as in the other reports on modal shift, pavement, compliance, and safety that comprise Volume II, none of the scenarios studied involve increases in weight for more than a single vehicle configuration. The analysis did not in any way consider the possible cost effects of the introduction of various combinations of the different alternative truck configurations in a single scenario.

With respect to the one-time structural costs, multiple alternative truck configurations would likely impact many of the same bridges identified as needing strengthening or replacement. Therefore, scenario cost summaries would overlap extensively with respect to specific bridges.

Table 27: Scenario 1-6 Summary
Empty Cell Interstate Highway System Non-IHS NHS Total
SCENARIO 1:
5 Axle 3-S2 (CS5)
GVW = 88,000 lbs.		 *One-Time Bridge Strengthening or Replacement Costs --- $0.4 B $0.4 B
SCENARIO 2:
6 Axle 3-S3 (CS6)
GVW = 91,000 lbs.		 *One-Time Bridge Strengthening or Replacement Costs --- $1.1 B $1.1 B
SCENARIO 3:
6 Axle 3-S3 (CS6)
GVW = 97,000 lbs.		 *One-Time Bridge Strengthening or Replacement Costs $0.6 B $1.6 B $2.2 B
SCENARIO 4:
5 Axle 2-S1-2 (DS5)
GVW = 80,000 lbs.		 *One-Time Bridge Strengthening or Replacement Costs $0.4 B $0.7 B $1.1 B
SCENARIO 5:
7 Axle 2-S1-2-2 (DS7)
GVW = 105,500 lbs.		 *One-Time Bridge Strengthening or Replacement Costs $0.5 B $0.2 B $0.7 B
SCENARIO 6:
9 Axle 3-S2-2-2 (DS9)
GVW = 129,000 lbs.		 *One-Time Bridge Strengthening or Replacement Costs $3.7 B $1.7 B $5.4 B
*Costs are in 2011 dollars, rounded to the nearest $100 Million. As noted in Section V of this report, the calculated one-time structural costs represent the "extreme upper bound of possible [bridge strengthening or replacement] costs. Return to footnote *

Observations

Assumptions

  • Annual Bridge Capital Costs are based on 2011 (base year) FMIS cost summaries, including both the State and Federal shares.
  • Bridge damage costs are equated to the total related repair and replacement project costs (inclusive of design, construction inspection, etc.).
  • Maximum legal weights for each truck class are used for structural analysis and for fatigue analysis.

Limitations

  • Costs derived for both the one-time structural related issues are independently investigated for each scenario. The costs for multiple scenarios are by the nature of the analysis not additive.
  • The reported one-time structural related costs represent an extreme upper bound.
  • Distortion induced fatigue in steel members is not included in the study.
  • While an extensive literature search was conducted and expounded upon, study schedule and time constraints only supported the detailed analysis of representative bridges.
  • Load and Resistance Factor Rating (LRFR) capability was not available in AASHTO’s ABrR software for the structural analysis of trusses and girder-floor-beam bridges (consequently, LFR was used for those bridge types).
  • Outputs from the modal shift modeling effort produced data that did not distinguish between intra-modal (truck-to-truck) and inter-modal (between modes) shifts.

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