ride quality: smooth sailing or fasten your seat belts?

307-213-0223 [email protected] Mike Robinson, PE307-213-0223 [email protected] Mike Robinson, PE

Ride Quality

California Asphalt Pavement Association – Sacramento – October 28-29, 2015

Smooth Sailing or Fasten Your Seat Belts?

Photo courtesy of Tom Massaro


The Case for Smoothness

• Lower fuel consumption• Less pollution• Less vehicle wear and tear and damage• Less damage to freight• Less pavement damage from vehicle

dynamics• Happier traveling public• More money for roads!!!


Why Now?

• Always have had some ride quality requirements– Buyer’s impression– Straightedge– Profilograph


International Roughness Index

• Improved technology makes it possible• FHWA initiative– Increase pavement life– Decrease user costs– Improve public perception


The Key Differences

• Measuring actual profile rather than looking for deviations over 12’ or 25’

• Simulating profile’s effect on vehicle response– Unsprung components– Suspension / vehicle / occupant response


About 7’ About 50’


The “Wheel Hop” End We Understand

• Shorter wavelength roughness is easy– Rotomill can take it out– Paver can take it out– Straightedge can find it (usually)– Profilograph can find it– Diamond grinder can find it


Longer Wavelength / Dynamics

• Longer than the tools we use• Can’t “see” them – Have to rely on ProVAL software

• Simulated vehicle dynamics affect the result


What It Boils Down To:The time, effort, and money spent to achieve a

given level of final ride quality depends on:

– The pre-construction ride quality for overlays– The number and types of opportunities for

improvement– The practices employed at each opportunity

It is no longer just a matter of grinding bumps after paving.


How Important is This Change?

• Disputes & Claims in the millions• Claim amount exceeding the original contract

amount• Grinding costs equivalent to adding an

additional 0.10’ overlay over the entire project


How Can You Succeed?

• Be aware of every opportunity for ride quality improvement

• Know best practices• Implement best practices• Monitor your work – know what you can and

cannot accomplish• Be concerned and willing to learn


Opportunities for Improvement

• Corrections applied to existing surface• Cold milling• Cold-In-Place Recycling• Intermediate lifts• Corrections applied to intermediate lifts• Final lift• Corrections applied to final lift


Leveling Course


Pre-paving Grind


Leveling Course Followed by Grinding


More than one removal option


What you pave on matters


Best Practices - General

• CONSISTENCY IS KEY• Maintain constant speed – DO NOT STOP– Milling– CIR– Paving


Best Practices - General• Balance operation– Mix production– Haul • To the paver, from the coldmill

– Paver / Coldmill speed– Compaction of mix• Hot• Warm• Cold



• Use as long an averaging reference as possible– Sensors at each end of the cold mill– Ski– Mat referencer– Long-wheelbase grinder

• Control cross-slope as well as profile



• Reference as smooth a surface as possible– Existing surface– Previously-ground or placed lane


Best Practices – Milling

• Consistent maintenance – Blocks and teeth– Referencing equipment– Machine in general

• May want fine or micro-milling, especially for single, thin overlays


Best Practices – Leveling Course

• Choose an appropriate mix• Make sure you have adequate time to

compact– Thin lifts cool very quickly – Multicool

recommended• Use pneumatic rollers– Steel drums will bridge


Best Practices – CIR

• Verify existing conditions for consistency• Have a choice to make:– Constant depth• More consistent material• Little to no ride quality improvement

– Variable depth – profile correction• Less consistent material• Can improve ride quality significantly

Photo courtesy of Darren Coughlin


Best Practices – CIR

• You can grind bumps on CIR– Make sure recompaction is good before grinding– May need to grind in cooler conditions (i.e. nights

or mornings)– Focus on high spots, not dips– Choose tool and timing carefully• Some have reported raveling of ground surface when

exposed to traffic for extended periods

• Remember – CIR is not HMAPhoto courtesy of Darren Coughlin


Best Practices – Paving

• Choose an appropriate mix• Control mix properties– Gradation– Binder content– Temperature– Segregation


Best Practices – Paving• Balance production / haul / placement /

compaction• Monitor time available to compact– Multicool– May need to adjust for changing conditions



• Minimize contact with the paver– Windrow paving– Material transfer device / vehicle


Best Practices – Paving• Avoid thermal and mechanical segregation in

the hopper– Either fold the wings after every load, or never fold

them– Do not run the hopper below half full


Best Practices – Paving• If end dumping– Do not back into the paver – let the paver pick up

the truck– “Break” the load before releasing the end gate– Flood the hopper



Do not allow material to overflow



• Set flow gates to allow for balanced flow and steady flight chain operation– If paver is not centered on pass, adjust

accordingly



• Use auger and tunnel extensions as necessary

• Use material management / anti-segregation baffles / chain curtains / etc.



Maintain a constant (and proper) head of material ahead of the screed



• Create as straight a joint as possible– Stringline and guide– If you cut the longitudinal joint back, cut it in a

straight line• Pave in constant widths as much as possible• If you have to adjust widths, do it slowly and

adjust material flow



• Minimize raking• Do not walk on the mat



• Do not park the rollers on the mat• Reverse roller direction at an angle• Control roller speed, particularly on turns



• Use a straightedge on construction joints• Leave enough manpower and material to

build the joint


Reasonable Expectations

• Ride quality after any given opportunity for improvement– Depends on the existing ride quality– Will generally be no better than about 60% of

pre-operation ride quality

• You results may vary – you need to know what you can accomplish.



• Leveling course– Generally less improvement than overlay– Can be improved with stringline / cuts & fills• Remember differential compaction

– You can grind or mill leveling courses



• Cold-In-Place recycling– MRI of 80 to 90 inches per mile is possible • Assuming good paving practices• Assuming good recompaction

Photo courtesy of Darren Coughlin



• Cold milling– About 60% of pre-milling ride quality is possible– Requires grade control and good reference– Requires grinding for ride, not production– May require fine or micro texture



• Bump grinding– Difficult to fix low spots– Deep grinds are slow, create more disposal, and

may run afoul of specifications– Longer wheelbase can help



• Paving– About 60% of pre-paving ride quality is possible– Can be considerably less if pre-paving ride quality is

high– Depends on paving practices used

Reasonable Improvement from FHWA FP-03:– Single lift – 12-25 inches/mile improvement– Multiple lifts – 34-43 in/mi improvementNew construction should yield 60-65 in/mi final MRI


Reasonable Expectations• ProVAL Smoothness Assurance Module– 2D simulation of a 3D situation– Assumes precise depth control of grinder– Grinder must be accurately input• Results for an 18’ wheelbase will not match the

simulation for a 25’ wheelbase grinder– Does not account for grinder wear, ability to

transition, tendency to ride out of cut, etc.– Accurate locations of grinds are essential – use GPS,

not just the DMI– Dependant on who runs the grinding simulation


So…

Be careful


So…

Pay attention to details


So…

• Look at what you are paving on• Look at every opportunity to improve ride

quality• Use best practices• Know what you can and cannot accomplish

ride quality: smooth sailing or fasten your seat belts?

Engineering