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

Objectives  Reasonable cost  Good data  Low maintenance  Long performance life

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

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

Site Selection Criteria- Power and Phone Availability 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- 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

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)

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

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

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

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

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

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

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

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

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

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)

WIM System Equipment  Functional requirements  Performance requirements  Warranty requirements  No “how it must be built” requirements

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

Bid document layout plan

Bid document details

Vendor specific configuration

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

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

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

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

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

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

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

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

In-Pavement Component Install- Comments on photos The steps displayed in these photos are general in nature and by no means cover all of the required steps and details for installation. Installation must conform to the WIM manufacturer’s requirements and should be supervised by the manufacturer’s representative.

Construction and Installation- Off Roadway Component Install  Power and phone facilities in accordance with:  plans  agency’s specifications  utility company’s requirements  electrical codes  Prepare as-built plans

WIM System Acceptance Testing  System component operation  Functional requirements  Accuracy requirements  weight  speed/axle spacing  Continuous operation testing  length of test period per agency requirements

WIM System Acceptance Testing- System Components On-site observations-  All loops, weighpads, and piezos (if utilized) sending signals  Controller electronics converting signals to specified data elements  “Real-time” WIM vehicles match observed  Determine extent of system errors vs. errors caused by “undesirable traffic conditions DOCUMENT! DOCUMENT! DOCUMENT!

WIM System Acceptance Testing- System Calibration  Initial system calibration is typically the responsibility of the installation contractor and/or the WIM vendor and is not, in itself, part of the agency’s “acceptance testing”  It is recommended that the agency observe the calibration process and copy all documentation for comparison to agency’s accuracy validation findings

WIM System Acceptance Testing- Accuracy  Agency uses test trucks to validate accuracy of weights, speed, and axle spacings  Truck types, static weighing and loaded weights, speed patterns, etc., in accordance with agency’s guidelines  Accuracies to be met in accordance with agency’s statistical requirements  tolerances typically from ASTM standard E1318

LTPP SPS requirements

CalTrans requirements

WIM System Acceptance Testing- Continuous Operation  All data for test period downloaded, processed, and analyzed  Determine that all system components are working well on continuous basis  Determine that all required hardware and software software meet performance requirements  communications  on-site  office

SYSTEM ACCEPTANCE Upon successful completion of the continuous operation testing, the system is accepted, the warranty period begins, and data collection commences HOWEVER

WIM System Monitoring The proper installation of a high quality WIM system is a major investment. Although such a system has the capability to produce research quality truck size and weight data, quality data will not be realized in the absence of proper operation, monitoring, and maintenance.

WIM System Monitoring  Routine downloading and storage of data  Processing, validation, and tracking of data  Monitoring and tracking calibration  on-site testing  traffic stream analyses  System troubleshooting checks  System maintenance  Data dissemination and archiving The agency should have procedures for:

Objectives- Revisited Although proper installation procedures are critical in order to attain all of these objectives, good data is attainable only with proper post-installation operation, monitoring, and maintenance procedures. 4 Reasonable cost 4 Good data 4 Low maintenance 4 Long performance life

QUESTIONS ? CONTACT: Rich Quinley