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Performance Based Practical Design
March 30th, 2016ITS Georgia
DOT’s face increasing challenges
• We learned from those who taught us how and why we follow the standards…
• There are valid reasons that tell us we now need to work differently:
• Funding• Staff Resources• Aging infrastructure• Environmental considerations• Availability of reliable data and information• Technology
Engineering Culture
PBPD is a decision making approach that helps agencies better manage
transportation investments and serve system-level needs
and performance priorities with limited resources.
What is PBPD?
• New Policy, Regulation, or Requirement• Opportunity to disregard long -term needs:
• For short term cost savings• Overlooking future development
• Compromising on safety, user needs (bike, ped, etc.), or accommodation of freight to save money
PBPD is not:
PBPD – Overlapping
Context Sensitive Solutions
Value EngineeringSystem Performance
Indiana’s Version of PBPD
Existing Typical 9’ Lanes 3’ Shoulders
Proposed Initial Typical 12’ Lanes4’ Paved Shoulder 4’ Aggregate Shoulder
11’ Lane 2’ Paved Shoulder1’ Aggregate Shoulder
Practical Design Example
Practical Design SavingsItem Original Cost Practical Cost Savings
Pavement DesignReduce driving lane from 12' to 11' $3,600,000 $3,300,000 $300,000
Minimize Underdrain Depth and locations $120,000 $60,000 $60,000
Shoulder DesignReducing shoulder Aggregate width 4' to 1' $160,000 $40,000 $120,000
Reduce to 3:1 Side Slopes and V-bottom ditches $775,000 $525,000 $250,000
UtilitiesRelocate 8" gas line to lower elevation $3,000,000 $500,000 $2,500,000
Move OH utilities inside Clear Zone:Reduce trees to be removed $232,000 $132,000 $100,000
Reduce area of mitigated wetlands $500,000 $400,000 $100,000
Reduce number of mitigated trees $50,000 $10,000 $40,000
StructuresModify instead of replace most large structures $700,000 $200,000 $500,000
Structure Removal $120,000 $20,000 $100,000 Minimizing Cover Depth at Crest Curves $40,000
Structure Backfill $60,000 $20,000 $40,000
TOTAL PROJECT SAVINGS: $4,150,000
Performance Based Practical Design Example
Performance Based Practical Design Example
Performance Based Practical Design Example
Interactive Discussion:Expanding Freeway Capacity
• Predictive safety comparing alternatives.• 125,000 AADT• Values are for a 6-mile segment only
considering a continuous freeway segment (no merge, diverge or weave)
Alternative
No. of General Purpose
LanesTotal K A B C PDO
254.4 0.9 2.6 18.6 54.2 178.1Full Build 4 12 12 12 12 12 12
201.310 293.9 1.3 3.1 22.9 65.3
63.4 210.1
Alt. 1 4 4 11 11 12 12
12 12 293.6 0.8 2.3 16.8
Estimated Crash StatisticsEstimated average crash freq. during Study
Period, crashes/yr:
Inside Shoulder Width Lane Width Outside Shoulder Width
NoBuild 3 12 12 12
K – at least one fatality occursA – at least one disabling injury occursB – at least one evident, non-disabling injury occursC – at least one possible injury occursPDO – no injury occurs but property damage in excess of the
state’s minimum reporting threshold occurs
Which One Would You Choose?
14
Total K A B C PDO
254.4 0.9 2.6 18.6 54.2 178.1
201.3293.9 1.3 3.1 22.9 65.3
63.4 210.1
293.6 0.8 2.3 16.8
Estimated Crash StatisticsEstimated average crash freq. during Study
Period, crashes/yr:
12’ 12’ 12’ 12’12’
11’ 11’ 12’ 12’ 10’4’
12’ 12’ 12’ 12’12’
12’ 12’ 12’ 12’12’ 12’
Can we make more out of our
alternatives?Can we have the best of both?
Before
Operational Benefits of Shoulder Running
15
After
Shoulder Use and Limitations of the HSM
16
When Do the Lowest Fatalities Occur on Urban Freeways?
17
AM Peak Period
PM Peak Period
Is this a Rutting Issue?A Cross-Slope Issue? Or Some Combination of Both?
Is this a Rutting Issue?A Cross-Slope Issue? Or Some Combination of Both?
Is this a Rutting Issue?A Cross-Slope Issue? Or Some Combination of Both?
Hydroplaning Predictive Analysis Results
43
44
45
46
47
48
49
50
51
0
100
200
300
400
500
600
700
800
900
1000
1100
1200
1300
1400
1500
Hyd
ropl
anin
g Sp
eed
(mph
)
Section Length (ft)
Rainfall Intensity: 6 in/hrRainfall Intensity: 6.972in/hrSpeed Limit
LiDAR with drainage path length modeled
Fixing This Is Expensive & ComplicatedEspecially When Bridges Are Involved…
Variable Speed Limits
• What if the following assumptions are “off”?• Traffic data• Crash predictions• User costs• Construction/materials costs
When you consider the risk of being “off” on your predicted performance calculations…
The chances the alternative will outperform the calculated B/C are about 10%.
The chances the alternative will UNDERPERFORM the calculated B/C is greater than 89%.
30 1 22.1
Calculated Benefit/Cost
ALL ENGINEERING CHOICES HAVE TRADE-OFFS
Cost
Valu
e (O
pera
tions
, Saf
ety,
Eff
icie
ncy
etc.
)
Min
imum
Sta
ndar
ds
Below Design Criteria
Meets or Exceeds Design Criteria
Same Cost, Better Value
Same Value, Lower Cost
Which One Would You Choose?
FHWA is prepared to support States as they develop projects with a
system performance mindset using data-driven methods
FHWA Will be a good partner
