California Department of Transportation

Project Development Workflow Tasks (PDWT)

Part 3 - Identify Project Need and Project Initiation Document

II. Project Initiation Document

B. Develop Initial Alternatives (WBS 150.10) - Develop Concept Alternatives (WBS 150.10.15)

P38. Request Pavement Deflection Study

A Pavement Deflection Study. assists in identifying rehabilitation options to achieve a 10-year-design life of exiting flexible (A/C) and rigid (PCC) pavement. The Division of Engineering Services – Office of Materials Engineering and Testing Services (DES-METS) perform Deflection Studies and provides recommendation regarding pavement rehabilitation strategies. All projects that involve rehabilitation of flexible and rigid pavement require a Deflection Study during PS&E to substantiate the final project structural section design. Presently, Deflection Studies are not required for (PIDs), but may be performed for projects involving asphalt concrete pavement overlay or concrete pavement doweling. If there is not sufficient time to obtain and use Pavement Deflection study results, the project engineer may assume an AC overlay thickness of 135mm. For high priority projects, a Deflection Study should be requested during the PID development even if the study results arrive after completion of the PID. In this case, PID cost estimates can be updated soon after programming. The June 7, 1999 memorandum by Robert L. Buckley and Randall H. Iwasaki spell out this policy. Pavement Deflection Study results are used as for preparing project pavement material quantity and cost estimates, which typically account for a significant portion of rehabilitation project construction costs. PIDs should be based on actual study results and assumed data avoided.

The project engineers must determine the most appropriate time to request a Deflection Study. The final structural section design used in a project PS&E must be based on a Deflection Study that is no older than 1 ½ years at the time the PS&E is submitted by the District to Headquarters Office of Office Engineer. Depending on the lengthiness of a project schedule, it may be necessary for the project engineer to request a second Deflection Study and to update the project design and cost estimates.

Deflection Studies are obtained by sending a memo request to the Region/District Materials Engineer. The project engineer must provide certain information to the Materials Engineer with the request including:

  • Project EA Number
  • Location where testing is needed (Co-Route & project limits)
  • Description of proposed work (Overlay, widening, etc.)
  • The target project PS&E submittal to HQOE date
  • The Design Designation & design life Traffic Index number
  • As-built records of the roadway typical section

Other special considerations may require Deflection Study recommendations. For instance, detours for projects widening two-lane roadways may require moving traffic onto the existing shoulders. The project engineer will need to know the existing shoulder pavement strength and the ability of that pavement to handle temporary traffic. This should specifically be noted this in the request. The project engineer will also need to provide the Traffic Index number for the year that the shoulder will be used as a lane, and will need to provide an estimate of the duration of the detour. When a relinquishment of a State facility to a local agency occurs, a Pavement Deflection Study is required to quantify what rehabilitation is necessary to bring the pavement up to “ state of good”.

As-built records containing information about the underlying layers of pavement materials may not be available for older highways that were adopted into the State’s highway system. The project engineer may then need to specifically request coring samples be taken during the Deflection Study. Coring samples can also help reveal the presence of unwanted sub layers of concrete or other materials that may affect constructibility, project construction costs, and the rehabilitation strategy.

Time Constraint:

Obtaining a Pavement Deflection Study. may take 4 to 6 months due to scheduling of tests against other requests made throughout the state. The project engineer should consult with the District Materials Engineer for an anticipated completion time.


HDM, (Chapter 600, Topic 611.9 “ACP Rehabilitation Strategies”)

PDPM, (Chapter 9, Article 5, “PSSR for Structure Rehabilitation and Pavement Rehabilitation Projects”)

Pavement Survey Evaluation Manual

Flexible Pavement Rehabilitation Manual

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This page last updated July 20, 2010