INSTALLATION OF WEIGH-IN-MOTION SYSTEMS

1. INSTALLATION OF WEIGH-IN-MOTION SYSTEMS by Rich Quinley April 2003 Rev. July 2004

2. Objectives • Reasonable cost • Good data • Low maintenance • Long performance life

3. Considerations • Site selection • Pavement preparation • WIM system equipment • WIM component layout and installation techniques • Power and phone layout and installation techniques • WIM system acceptance testing

4. Site Selection Criteria • Access to power and phone • Adequate location for controller cabinet • Adequate drainage • Traffic conditions • Roadway geometrics • Roadway grade • Existing pavement profile and structural condition

5. Power: AC vs. solar Conduit installation cost Reliability Phone: Land line vs. wireless technologies Conduit installation cost Equipment installation cost Data transfer rate Operation cost Reliability Site Selection Criteria-Power and Phone Availability

6. Site Selection Criteria-Controller Cabinet Location • Protection from vehicles leaving roadway • Accessible and safe for users • Good visibility of roadway • sensors • approaching vehicles • Short conduit runs to loops and weighpads

7. Site Selection Criteria-Adequate Drainage • Cabinets and pullboxes on high ground • Ability to drain weighpad channels and maintain drainpipes • “daylight” drainpipe at embankment slope (best), or • tie drainpipe into existing facility, or • run drainpipe into sump (least desirable)

8. Site Selection Criteria-Traffic Conditions Desirable • All vehicles centered in each lane at “cruising” speeds Avoid • Stop and go traffic • Slow moving traffic • more difficult to calibrate • Lane changing, including two-way passing

9. Site Selection Criteria-Geometrics and Grade • Tangent section of roadway • Adequate lane widths • Consider proximity of interchanges, intersections, on/off ramps, etc. • Good sight distance • Avoid roadway grade > 1% • more difficult to calibrate • more difficult to monitor calibration • effects weight transfer from steer to drive axle

10. Site Selection Criteria-Existing Pavement Evaluation Approach roadway • Minimum 500’ with smooth profile • more specific requirements for LTPP SPS (“long wavelength”) • Pavement structurally sound and in stable condition

11. Site Selection Criteria-Existing Pavement Evaluation Pavement through WIM system • If existing pavement is PCC, determine: • grind only or replace • if replace, extent of replacement • If existing pavement is asphalt, determine: • extent of replacement with PCC

12. Other Site Selection Recommendations • Observe traffic flow at various times of day for “undesirable” conditions • Observe truck traffic • “cruising” vs “lugging” • staying in lane • Consult with individuals who have knowledge of traffic at site • Verify that there are no plans to widen or perform pavement rehab

13. Site Selection Criteria-Summary Typically rare to find a section of roadway within a specified route segment that meets all “ideal” criteria for a WIM location, particularly in urban areas

14. Site Selection Criteria-Summary Site reviewer must consider tradeoffs, based upon the importance of the site, as to the effects that a site’s location will have in terms of: • Data quality • Cost to install • Construction problems • Maintenance of roadway and WIM system

15. Pavement Preparation Criteria • If existing PCC pavement is structurally sound with smooth profile- • grind 200’ in advance and 75’ following scale location* • If existing PCC pavement is unstable and/or rough, or if existing pavement is AC- • replace pavement and grind* * more specific requirements for LTPP SPS

16. Pavement Replacement Criteria • Replacement length per agency • 400’ minimum per LTPP SPS • 150’ - 250’ per Caltrans • Replace existing pavement and first level of base material- minimum 12” depth PCC • Seven sack concrete mix with accelerator • can typically open to traffic 4 hours after application of curing compound

17. Grind New PCC Slab Criteria • For new concrete slab within existing PCC pavement- • start and end grinding in existing pavement as needed to meet smoothness requirements but not less than 25’ preceding and 25’ following new concrete slab • For new concrete slab within existing AC pavement- • start grind 25’ preceding new concrete slab and end 25’ following new concrete slab • seal ground AC (per agency requirements)

18. WIM System Equipment • Functional requirements • Performance requirements • Warranty requirements • No “how it must be built” requirements

19. WIM Site Layout, Plans, and Installation Details Intent • Simplify construction • Maintain structural integrity of roadway • Simplify maintenance of power and phone facilities • Simplify replacement of roadway components

20. Bid document layout plan

21. Bid document details

22. Bid document details

23. Bid document details

24. Bid document details

25. Bid document details

26. Vendor specific configuration

27. Construction and Installation • Pavement replacement (If required) • Pavement grinding • Component layout • Sawcutting for in-pavement components • Pavement “cutouts” for scale frames • In-pavement component installation • Off-roadway component installation

28. Construction and Installation-Concrete Pavement • Determine limits of pavement replacement • Agency’s specifications for concrete mix and placement requirements • Weakened plane joints - CRITICAL! • Determine weakened plane joint layout to accommodate WIM vendor’s component layout requirements

32. Construction and Installation-Sawcut Weakened Plane Joints • Cut ASAP following PCC pour • no raveling or spalling • Joint spacings per agency’s specs • recommend avoid >16’ • Skew per agency’s specs • install perpendicular for panels containing scales and loops for best fit • Depth per agency’s specs • cut 1/2 PCC slab depth both sides of scale location

34. Construction and Installation-Pavement Grinding • Determine limits of pavement grinding • Grinding machine requirements • diamond cutting blades • minimum grind width 3’ per pass • residue pickup vacuum • Check ground pavement for conformance to smoothness requirements

36. Construction and Installation-In-Pavement Component Layout • Determine bending plate and loop locations considering: • WIM vendor’s specifications • weakened plane joints (new joints vs. existing joints) • Establish perpendicular control • 12’ x 16’ x 20’ triangle • Mark all sawcuts for loops, home runs, and scale frames on pavement

38. Construction and Installation-Sawcutting for In-Pavement Components • Proper depths • Proper slot widths for loops and home runs • Additional cuts for loop and homerun conduits across joints

40. Construction and Installation-Concrete Removal for Scale Frames • Jackhammer or rockwheel • Take care not to spall edges • Control depth!!! • Overcutting: • weakens pavement • increases epoxy quantity • increases difficulty of frame installation

45. Construction and Installation-In-Pavement Component Install • WIM vendor’s specifications • Vendor’s representative on-site • Epoxy at proper temperature • Frame pit clean and dry • Anchor holes clean • All conduits sealed • Loop slots clean and dry • Before set weighpads: • conduits and drains clear • pullrope in place for install adjacent lane