Transcript 2008 Davis

REDUCING ENGINEERING STANDARDS:
GOOD or BAD?
AASHTO Subcommittee on Design
Albuquerque, NM
July 14, 2008
ILLINOIS EXPERIENCE – Widening &
Resurfacing Program of early 1970’s
Widened many miles of 18-foot and 20 foot 2lane highways to 24-feet (two 12-foot lanes)
Minimal shoulders – avoided additional ROW
Almost no alignment improvements (horizontal or
vertical)
Eliminated concrete lip curbs
Widened and/or replaced narrow bridges
Upgraded traffic signals – added breakaway bases
Created and/or expanded clear zone – eliminated
fixed objects to the extent practical
NO DOUBT IN MY MIND – WE SUBSTANIALLY
IMPROVED SAFETY – even though we did not
meet all minimum standards
3R (RRR) Rulemaking Experience
1976 – Congress redefines “Construction”
to include 3R’s – resurfacing, restoration
and rehabilitation
AASHTO 3R Design Standard (Purple
Book)
FHWA 3R Design Standards
Ultimate 3R Rulemaking (now 23 CFR
625.4)
3R (RRR) Rulemaking
Based primarily on a major research
effort conducted by FHWA that
concluded that:
Greater overall safety can be achieved
by improving more miles of highways to
lesser standards than by improving a
few miles of highway to full standards.
ARIZONA EXPERIENCE – since
1984
Generally achieve full standards on new or
full reconstruction projects
Arizona (ADOT) has not exercised the option
of adopted separate standards for 3R
Projects.
We are encountering many deviations as we
improve existing highways – including our
Interstate highways
We are using the Design Exception process
The Dilemma – to reduce
standards or not
Even with my experience with 3R efforts
involving improvements that do not achieve
or meet all standards, I am reluctant to
actually reduce design standards.
I believe the Design Exception process
provides an opportunity to fairly and
objectively review and justify deviations
My primary concern – the public is driving
our highways at ever increasing speeds
Higher Speeds – My Concerns
Public appears to be very comfortable driving at
speeds above 70 mph – at 80 and even 90 mph –
even in heavy traffic
This exceeds the Design Speed used for most
existing highways
Modern vehicles and tires appear capable of these
higher speeds
Modern suspensions mask some sensations of high
speed
Unfortunately, I am not sure driver skills are able to
effectively deal with this high speed – when
something goes wrong (most of us are not NASCAR
drivers)
Maintaining high design standards is our best hedge
against this tendency toward higher speeds