AASHTO Subcommittee on Design
July 14, 2008
David C. O’Hagan, PE
Florida DOT State Roadway Design Engineer
REDUCING ENGINEERING
STANDARDS: GOOD OR BAD?
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
DOT’s Costs: Pre-construction, right of
way, construction, maintenance.
Maintenance: Insignificant differential.
User Costs: Safety
AASHTO VS PPM
OPTIONS
1. Maintain Status Quo: Use Variations Process to
justify reduced criteria
2. Reduce PPM Criteria: Eliminates need for some
Variation submittals
3. Revise Variation Requirements: Include a safety
analysis to quantify impacts of reduced criteria.
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).
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%)
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
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
SR 43 (US 301): Balm Rd to
Gibsonton Dr.
As designed
 Construction:
$82,200,000
 Right of Way: $10,200,000
(Ponds)
 DOT Costs: $92,400,000
 Crash (20 yr): $95,600,000
 DOT+User Costs (20 yr):
$188,200,000
PPM Design
 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%)
DOT+User Costs (20 yr):
$197,300,000 (+5%)
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
SR 50: US 19 TO CR 587
AS DESIGNED
 Construction: $49,200,000
 Right of Way: $0
 DOT Costs: $49,200,000
 Crash(20 yr): $85,600,000
 DOT+User Costs (20yr): $134,
800,000
PPM DESIGN
 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%)
DOT+User Costs (20yr):
$137,200,000 (+2%)
* $32,800,000 if open conveyance &
excluding business damages.
SAFETY IMPACT DIFFERENCES
 SR 43 (Hillsborough)
Side Slope:
SR 50 (Hernando)
Side Slope:
 HSM: +$6.6M
 HSM: +$6.0M
 RSAP: +$9.4M
 RSAP: +$9.7M
Median Width:
 HSM: +$1.0M
 DOT Research: +$3.0M
Combined:
 HSM: +$7.6M
Median Width:
 HSM: +$0.5M
 DOT Research: +$0.5M
Combined:
 HSM: +$6.5M
Accident Modification Factors
 Undivided
Divided
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