Two trucks approaching the same weigh station can receive different instructions even when there is nothing obviously different about them from the driver’s perspective. One may get the bypass while the other is directed in, and the decision can be influenced by information enforcement already has before either truck reaches the scale.
There is no single nationwide formula that determines whether an individual truck will be inspected. States use different roadside screening systems and selection procedures, while inspectors can also identify vehicles based on visible defects or established inspection-selection criteria.
Behind many of those decisions, however, is a federal tool designed to help enforcement determine where inspection resources may be most useful.
ISS Helps Prioritize Carriers for Inspection
FMCSA’s Inspection Selection System, or ISS, is used at roadside inspection locations to help enforcement personnel identify and prioritize motor carriers for safety inspections.
For carriers with sufficient safety data, the system draws on FMCSA safety information, including roadside violations and state-reported crashes. ISS then assigns an inspection value from 1 to 100 along with one of three recommendations: Inspect, Optional or Pass.
An Inspect recommendation represents the highest inspection priority, while Optional falls into the next level. A Pass recommendation indicates that available safety information does not suggest inspection resources should be prioritized toward that carrier.
Those recommendations are not guarantees. A Pass does not give every truck operated by that carrier an automatic bypass, just as an Inspect recommendation does not mean every vehicle will receive a full inspection each time it encounters enforcement.
ISS is one source of information used in the selection process, not the entire process.
Carriers With Limited Inspection History Can Still Receive Attention
A carrier does not need a long history of violations to receive a higher inspection priority.
FMCSA uses a separate ISS calculation when there is not enough safety information available to evaluate a carrier through the usual process. That calculation considers the size of the carrier and how many inspections it has received during the previous two years.
The purpose is to encourage inspections that provide enough information to eventually evaluate the carrier based on its actual safety performance.
That means a newer carrier, or one with relatively little roadside inspection history, can receive an Inspect recommendation because FMCSA needs more information about its operations rather than because the carrier already has a poor safety record.
Electronic Screening Adds More Information Before the Truck Arrives
ISS becomes one part of a larger decision at locations using electronic screening.
FMCSA’s e-screening framework allows participating states to identify an approaching commercial vehicle, retrieve information about the carrier and vehicle and determine whether it should stop or bypass the facility.
The information considered can extend beyond safety history. Electronic systems may check operating credentials and other compliance information, while locations equipped with weigh-in-motion technology can screen vehicle weight before the truck reaches a static scale.
The technology used to identify a truck also varies. Electronic screening can involve transponders and other wireless systems, and some locations use license-plate or USDOT-number readers as part of their roadside setup.
Once the available information has been checked against the state’s screening criteria, the truck can receive instructions to continue or pull in.
As a result, a carrier’s safety record may favor a bypass while another issue, such as a credential or weight concern, still results in the truck being directed into the facility.
Random Selection Is Still Part of the System
Even when the safety information, credentials and other electronic checks are clear, a bypass is not guaranteed.
FMCSA’s electronic-screening model specifically includes random inspection selection. A vehicle that would otherwise qualify to continue can still receive instructions to stop because it was selected randomly.
That helps explain why a driver who routinely receives bypasses can suddenly be called in without any known change to the carrier’s safety record.
It also means drivers should be careful about drawing conclusions from a single pull-in. Being directed to a station does not by itself indicate that a carrier’s ISS recommendation has changed or that enforcement has identified a violation.
Inspectors Are Not Limited to What the Screening System Says
Electronic screening does not replace what enforcement personnel can see on the road.
FMCSA’s guidance for state motor carrier safety programs recognizes both established inspection-selection criteria and visible defects as ways commercial vehicles are identified for inspection.
That leaves room for an inspector to direct attention toward a truck when there is an observable reason to do so, regardless of whether electronic information would otherwise make the carrier a lower inspection priority.
This is also one reason the process can differ between locations. A fixed facility with electronic identification and weigh-in-motion equipment has different screening capabilities from a roadside inspection operation without the same technology.
The underlying goal remains the same: use available information and enforcement resources to identify commercial vehicles and carriers that warrant a closer look.
States Do Not All Screen Trucks the Same Way
FMCSA provides national safety information and supports the systems states use to exchange commercial vehicle data, but roadside enforcement remains a state and local function.
The agency’s Innovative Technology Deployment program specifically supports states in using safety and credential information to determine which commercial vehicles should be pulled in and which can bypass.
The equipment behind those decisions continues to vary. Some sites rely primarily on carrier identification and safety information, while newer projects are combining several screening technologies.
For example, FMCSA has funded an e-screening project at Maine’s Pittsfield Weigh Station that includes license-plate and USDOT readers, weigh-in-motion equipment and flat-tire detection. A separate South Dakota project on Interstate 90 is intended to expand electronic screening so compliant carriers can bypass the weigh station.
Those projects illustrate why a driver’s experience can change from one state, corridor or inspection site to another. The data available to enforcement and the technology used to evaluate it are not identical everywhere.
A Pull-In Does Not Tell You Why You Were Selected
From the driver’s seat, there may be no way to know which part of the process resulted in a particular instruction.
The carrier’s ISS information may have contributed. The truck may have been selected randomly, a credential may have required verification, weight screening may have triggered the stop or an inspector may have identified a visible reason to take a closer look.
That also explains why trucks from the same carrier do not necessarily receive the same instruction every time they encounter a weigh station.
ISS is designed to help prioritize inspection resources, while electronic screening gives states additional information to use before a truck reaches an inspector. Neither creates a permanent pass for carriers with stronger safety records.
The result is a selection process that can combine federal safety information with state screening criteria and conditions involving the individual vehicle. The green light or pull-in signal a driver sees is simply the final instruction from a process that may have started well before the truck reached the station.
Frequently Asked Questions
What do the ISS recommendations mean?
FMCSA assigns Inspect, Optional or Pass recommendations. Under the documented ISS algorithm, values from 75 to 100 correspond to Inspect, 50 to 74 to Optional and 1 to 49 to Pass.
Can a driver look up a carrier’s ISS value?
ISS values are not available to the general public. FMCSA states that a motor carrier can access its own ISS information by signing into the FMCSA Portal.
Can a carrier with a Pass recommendation still be pulled in?
Yes. An ISS recommendation is only one component of inspection selection. Electronic-screening systems can use additional criteria, and FMCSA’s screening model allows random selection.
Can a carrier be prioritized because it has very little inspection history?
Yes. FMCSA uses an insufficient-data calculation for carriers without enough information for the normal safety-based ISS calculation. Carrier size and the number of inspections during the previous two years are among the factors considered.
Can weigh-in-motion affect whether a truck is directed into a station?
At locations equipped with the technology, yes. Weigh-in-motion systems can screen a commercial vehicle’s weight while it is approaching the facility, allowing a potential weight issue to be identified before the truck reaches a static scale.
