Reducing Engineering standards: GOOD OR Bad

1
Reducing Engineering standards GOOD OR Bad?

• AASHTO Subcommittee on Design
• July 14, 2008
• David C. OHagan, PE
• Florida DOT State Roadway Design Engineer

2
AASHTO vs ppm

• SITUATION
• AASHTO Greenbook
• FDOT Plans Preparation Manual (PPM)
• GOAL
• To reduce the cost of DOT projects without
  sacrificing safety and operational/functional
  characteristics.
• ANALYSIS
• DOTs Costs Pre-construction, right of way,
  construction, maintenance.
• Maintenance Insignificant differential.
• User Costs Safety

3
AASHTO VS PPM

• OPTIONS
• Maintain Status Quo Use Variations Process to
  justify reduced criteria
• Reduce PPM Criteria Eliminates need for some
  Variation submittals
• Revise Variation Requirements Include a safety
  analysis to quantify impacts of reduced criteria.

4
AASHTO VS PPM

• RECOMMENDATION
• Option 3 Require a safety analysis with Design
  Variations for all new and reconstruction
  projects when reductions in critical design
  elements are being considered.
• JUSTIFICATION
• Variations Process already working well.
• Means to quantify safety impacts of cross-section
  decisions.
• Consistent with including non-DOT costs in our
  decisions (user costs in pavement-type
  selection).

5
AASHTO vs. PPM

• 2007 Study by Roadway Design Office
• Construction Cost Differences Only
• Interstate Widening (1.2)
• New Rural Freeway (8)
• New Rural Arterial (7)
• New Urban Arterial (10)
• New Overpass (21)

6
AASHTO vs. PPM

• 2008 Study by Roadway Design Office
• Include right of way and maintenance costs with
  construction costs.
• Rural Arterial Widening
• Urban Arterial Widening
• Interstate Widening
• New Overpass Construction

7
SR 43 (US 301) Balm Rd to Gibsonton Dr.

• Hillsborough County, 6.16 miles
• Currently Two-lane rural
• New Design Six-lane rural with sidewalk and
  shared-use path.
• Design at 90 Complete when studied
• Several Variations to eliminate ROW acquisition
  for typical section

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SR 43 (US 301) Balm Rd to Gibsonton Dr.

• As designed

• PPM Design

• Construction 82,200,000
• Right of Way 10,200,000
• (Ponds)
• DOT Costs 92,400,000
• Crash (20 yr) 95,600,000
• DOTUser Costs (20 yr) 188,200,000

• Construction 82,800,000 (0.7)
• Right of Way 26,300,000 (158)
• DOT Costs 109,100,000 (18)
• Crash (20 yr) 88,000,000 (-8)
• DOTUser Costs (20 yr) 197,300,000 (5)

10
SR 50 US 19 TO CR 587

• Hernando County, 3.73 miles
• Currently Four-lane rural
• New Design Six-lane rural with sidewalk and
  shared-use path.
• Design at 30 Complete when studied
• Several Variations to eliminate ROW acquisition
  for typical section
• Closed conveyance drainage system

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SR 50 US 19 TO CR 587

• AS DESIGNED

• PPM DESIGN

• Construction 49,200,000
• Right of Way 0
• DOT Costs 49,200,000
• Crash(20 yr) 85,600,000
• DOTUser Costs (20yr) 134, 800,000

• Construction Cost 58,100,000 (18)
• (Walls were 17)
• Right of Way 0
• DOT Costs 58,100,000
• Crash(20 yr) 79,100,000 (-8)
• DOTUser Costs (20yr) 137,200,000 (2)
• 32,800,000 if open conveyance excluding
  business damages.

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SAFETY IMPACT DIFFERENCES

• SR 43 (Hillsborough)
• Side Slope
• HSM 6.6M
• RSAP 9.4M
• Median Width
• HSM 1.0M
• DOT Research 3.0M
• Combined
• HSM 7.6M

• SR 50 (Hernando)
• Side Slope
• HSM 6.0M
• RSAP 9.7M
• Median Width
• HSM 0.5M
• DOT Research 0.5M
• Combined
• HSM 6.5M

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Accident Modification Factors

• Undivided

• Divided

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CONCLUSIONS

• Rural Widening
• Cost Savings are in ROW not construction.
• Variations procedure working well.
• AASHTO minimum criteria has significant safety
  impacts.
• Recommend including typical section safety
  analysis in Variation process for non-3R projects.

• Additional Work
• Study Urban Interstate Widenings
• Study Overpasses
• Review crash data of AASHTO-only states compare
  to Florida