♫ music ♫
Vehicle weigh-in-motion - WIM data is an integral part of traffic data.
It offers critical information related to the design, operations, and management
of pavement, bridge, freight, and safety of our transportation system.
FHWA has prepared a three-part set of pocket guides providing detailed,
technical knowledge and best practices on how WIM activities can be carried out effectively and efficiently.
Part 1 of the pocket guide deals with WIM Technology Selection, Data Acquisition Requirements, and Procurement
and its target audience is WIM program managers and WIM program-level decision makers.
Part 2 deals with WIM Site Selection, Design, and Installation and is targeted
to traffic engineers, senior WIM specialists, and WIM site-level decision makers.
WIM Maintenance and Calibration is the subject of part 3 and is
targeted to technicians involved in routine WIM maintenance and calibration activities.
These pocket guides can be found on the FHWA's Office of Highway Policy Information website.
The companion videos provide WIM professionals
a practical sense with installation of WIM sensors.
This instructional video will show you how to install the Quartz Piezo Weigh-In-Motion Sensor.
The procedures shown in this video are recommended best practices and are
not meant to circumvent the manufacturer's installation specifications.
[ large truck braking and horn sound effect ]
Several installation topics will be covered in this video.
We'll show you how to prepare and lay out the sensor,
explain proper saw-cut procedures, show how to mix and pour the grout,
and how to grind the sensor to maintain road smoothness.
A list of installation steps and a quality assurance checklist will be provided for each topic.
In preparation, here's a list of the tools that are needed. This list is not all-inclusive.
The manufacturer's installation guide and other project documentation
should be referenced for more detailed information and additional preparation requirements.
♫ music ♫
The materials list may also be available in the
manufacturer's installation manual, which may contain a list of additional
materials that are needed for installation beyond what is provided in this video.
♫ music ♫
It is imperative that all construction crew members wear proper personal protection devices
and are briefed on the various hazards associated with working near traffic and in industrial environments.
The use of a traffic spotter while working near active traffic lanes is highly recommended.
♫ music ♫
The installation begins with "sensor layout".
First, determine the correct location for the sensor installation.
Create a reference line, perpendicular to the outside pavement marking.
Measure the locations of the sensors using the reference line and paint the lines to be cut on the pavement.
A line perpendicular to the lane or pavement edge serves as a reference line for the sensor layout.
Use the properties of similar right triangles to assure that the line is perpendicular.
At the desirable sensor location,
make a mark on the inside edge of outer pavement marking.
From the original mark, walk straight into the travel lane and place additional marks
at 3 feet, 6 feet, and 9 feet from the original mark.
Next, walk along the pavement edge and place additional marks along the inside edge of the lane,
marking at 4 feet, 8 feet, and 12 feet from the original mark.
Extend the tape from the 4-foot mark toward the 3-foot mark,
measure to 5-feet and draw an arc that intersects the 3-foot mark.
Extend the tape from the 8-foot mark toward the 6-foot mark,
measure to 10 feet, and draw an arc that intersects the 6-foot mark.
Extend the tape from the 12-foot mark toward the 9-foot mark,
measure to 15 feet, and draw an arc that intersects the 12-foot mark.
Once all of the marks are drawn, there will be three sets of "X"s in the lane.
Starting at the original mark, extend a string across the travel lane intersecting each "X".
This is a perpendicular reference line.
Spray paint over the string or rope to create the perpendicular guideline to follow during sensor slot cutting.
Remember these three tips for quality assurance.
First, ensure the layout of the sensor is perpendicular to the pavement markings
by verifying the proper use of the right triangle method when creating the reference line.
Ensure that ambiguous paint marks are crossed out or blacked out to avoid confusion.
All sensor pavement cut measurements should match what is documented in the contract,
and must follow manufacturer installation guidelines.
♫ music ♫
The next topic is "exit hole installation". This includes four steps.
First, determine the location of the exit holes, typically 18 inches, to avoid pavement edge cracking.
Next, drill the exit holes using an appropriately sized rock drill bit,
typically one and a half inch in diameter.
Install the PVC and then plug or cover the conduit.
The rock drilling will go straight down for approximately one inch,
and then tilt out toward the conduit trench at 45 degrees or less.
Drilling continues until the bit exits into the trench. Then the drill is removed.
Conduit is installed through the exit hole using the side of the hammer.
A paper towel or rag is placed in the conduit or may be covered with duct tape
to keep debris from entering during the pavement cutting phase.
To ensure the exit hole is properly installed, follow this checklist.
Ensure the exit hole is located at the proper distance from the pavement edge,
and is in line with the sensor layout.
That the exit hole is drilled to the proper diameter, typically one and a half inches,
and at the proper angle, normally 45 degrees or less.
Verify that the top of the exit hole conduit is installed to at least
four inches below the pavement surface.
Once the conduit is installed, be sure to
plug or cover the conduit to prevent debris from getting inside.
♫ music ♫
The third topic is "saw cutting" and includes three steps.
First, align the saw blade with the painted markings.
Then, slowly lower the blade into the pavement to the specified depth.
Finally, cut along the pavement markings from the start point
to the end point, over cutting enough to allow proper depth at each end.
Use a depth gauge to check the slot cut depths.
Lower the blade into the pavement at the specified depth.
If wet cutting, make sure the water is running to keep
the dust minimized and the blade cool during operation.
If water is not being used, ensure that the operator is wearing a dust mask
and use clean, pressurized air to blow the dust away from the workers and traffic.
Cut along the painted layout, keeping the blade as straight as possible.
Over cut the proposed location of the sensor at each end to ensure the blade has met
the minimum depth where the sensor will be placed.
Use a depth gauge to make sure that the entire slot is cut to the proper depth.
Be sure you can answer "yes" to these three questions
to achieve sensor saw cut quality assurance.
Is the blade the correct size? Are all the saw cuts at the proper depths?
Are the saw cuts straight and along layout painted markings?
♫ music ♫
"Sensor channel preparation" is the fourth topic.
For this step, remove pavement material from the channel to the proper width and depth.
Then blow remaining debris out of the channel and the lead-in slot.
Clean the channel with a high-pressure washer or denatured alcohol,
and then dry the channel and slots with clean, pressurized air
until all moisture is gone.
Place duct tape on both sides of the sensor channel.
To ensure proper adhesion of the sensor grout
either clean the channel and slots with a pressure washer,
moving side-to-side and away from traffic until all solid debris has vacated the slot,
or with a residue free cleaner, such as denatured alcohol and a clean cloth.
Dry the channel and slots with clean pressurized air until all standing water is gone.
Place duct tape on both sides of the sensor channel.
For quality assurance, ensure the sensor channel and all slots are clean and dry, and that no standing water remains.
Duct tape should be placed on either side of the channel.
♫ music ♫
Topic five is "sensor preparation".
After carefully removing the sensor from the box,
inspect and test the sensor. Assemble the sensors and install grounding devices.
Install the leveling aids at each end and in the center of the sensor.
Place the sensor in the slot to ensure it properly fits before pouring grout.
Remove the sensor and place beside the slot.
Clean the sensor with isopropyl alcohol.
Mark each sensor lead with colored tape.
Carefully uncoil the lead-in and pull the sensor lead through the exit hole and conduit, and push the lead-in to the bottom of the slot.
Place backer rod in the saw cut to hold the lead-in down.
Finally, seal the exit hole to prevent backflow of grout or sealant.
After carefully removing the sensor from the box, the sensor is inspected and tested.
The sensors are assembled. Ground lugs and wires are installed to protect the sensor from power surges.
Leveling aids are secured at each end and in the center of the sensor.
The sensor is placed in the slot to ensure that it properly fits before pouring grout.
The sensor is removed and placed beside the slot.
The sensor is cleaned with denatured alcohol.
Each sensor lead is marked with colored tape.
After carefully uncoiling the lead-in, the lead-in is pulled through the exit hole and conduit,
and the lead in is pushed to the bottom of the slot with a blunt instrument.
Backer rod is placed in the saw cut to hold the lead-in down.
Finally, the exit hole is sealed to prevent backflow of grout or sealant.
To ensure that the sensor has been properly prepared and protected prior to installation,
be sure you can answer "yes" to these questions.
Were the sensor leads carefully handled when being uncoiled?
Was the sensor inspected and electronically tested prior to installation?
Were grounding devices and leveling devices properly installed?
Was the sensor pre-fitted into the slot to ensure that it fits properly?
Was the sensor cleaned?
Was the sensor lead properly marked and carefully pulled through exit hole and conduit?
Was backer rod placed in the saw cut to hold the lead in the slot?
Was the exit hole sealed?
♫ music ♫
Topic 6 is "grout mixing and pouring". Here are the steps.
First, determine if the pavement and ambient temperatures are conducive to installation.
Heat the grout, if necessary.
Mix the grout per manufacturer instructions.
Pour the grout into the slot up to one inch from the top
Use a trowel to sweep the grout up on both sides of the slot.
The crew leader will verify that the pavement and
air temperatures are conducive to sensor installation.
The installation QA inspector should make note of these values and verify they are correct.
The grout may need to be heated before use.
Once the grout has been mixed to manufacturer instructions,
pour it into the slot housing the sensor to within one inch of the pavement.
Be sure you can answer "yes" to these questions for grout mixing and pouring quality assurance.
Are ambient, chemical, pavement temperatures conducive to proper installation of sensor?
Were the chemicals mixed according to the manufacturer's recommended process?
Was the grout poured into the slot up to one inch from the top of the slot?
Was the grout swept up on both sides of the slot?
♫ music ♫
Now it's time to install the sensor.
Position the sensor in the slot and press down until the leveling aids make contact with the pavement.
Place weights on top the leveling aids.
Remove excess grout from the top of the sensor and the roadway.
The sensor is set in the slot and pressed down until the leveling aids
are making contact with the pavement,
ensuring that the leveling aids are holding the sensor in place and the sensor is not angled in any direction.
Weights are placed on top of the leveling aids to hold the sensor down.
Excess grout is removed from the top of the sensor and the roadway before it hardens.
To ensure quality during the sensor installation, follow these tips.
It is important that the sensor is set at the same height along the entire length of the sensor.
The leveling aids must be in contact with the pavement and cannot become
loose or fall off and the sensor must not be angled in the slot.
♫ music ♫
Topic 8 is "grout curing and grinding". Here are the steps.
Be sure the grout cures for at least one hour.
Longer waiting periods may be necessary in cooler temperatures.
Pull the tape away from the pavement and grout.
Remove the weights and leveling aids.
Cut any leveling aid straps flush with the pavement, if exposed.
Use a belt sander or diamond grinder to grind the top of the sensor
until it's completely flush with the pavement surface.
Blow the grout clean with pressurized air or sweep with a broom.
Verify the height of the grout using an aluminum bar and regrind as necessary.
Remove the backer rod. Fill slots with loop sealant. Scrape away excess material.
The crew will pull the tape away from the pavement and grout.
The raised grout will then be ground down with a belt sander or diamond grinder
until flush with the pavement.
The inspector should observe the crew leader checking the height
of the grout with an aluminum bar.
Once the sensor has been ground flush, it will be cleaned off
with pressurized air or swept off with a broom.
The backer rod is removed from the end of the slot near the exit hole.
At this point, loop sealant is used to cover the wire lead going into the exit hole.
Fill the slot flush to the pavement with sealant and allow it to cure.
More sealant is added if needed.
Once the sealant is cured, any excess grout or sealant will be scraped flush
to the height of the pavement.
Here is a list of quality assurance tips for grout curing and grinding.
Be sure the grout cures for at least 1 hour or as recommended by the manufacturer.
The sensor must be ground with a belt sander or diamond grinder to make sure it is flush with the pavement.
The smoothness of the sensor must be consistent along the entire length of the sensor.
The grout or sealant used to seal the homerun must be mixed properly
The homerun channel should be filled so that it''s flush with the pavement surface.
The information presented in this video will ensure that the sensor is properly installed
by demonstrating each of the critical steps involved and providing several quality assurance checks for each step.
The proper installation of the Quart Piezo sensor will extend the service life of the sensor,
and ensure a higher level of WIM data quality for the life of the WIM system.
♫ music ♫