When the Federal Motor Carrier Safety Administration (FMCSA) first rolled out its CSA (Compliance, Safety, Accountability) program in 2010, it was known as CSA (Comprehensive Safety Analysis) 2010. "2010" has subsequently been dropped and the program name changed.
A centerpiece of CSA is the new Safety Measurement System (SMS) methodology which is used to score carriers. The SMS organizes safety performance into seven in Behavior Analysis and Safety Improvement Categories (BASICs): Unsafe Driving, Fatigued Driving, Driver Fitness, Controlled Substances/Alcohol, Vehicle Maintenance, Cargo-Related and Crash Indicator.
The methodology for the SMS, contained in a 123-page document, details and quantifies how the SMS score is calculated for each carrier.
The document, published by the FMCSA, can be downloaded at csa.fmcsa.dot.gov/about/basics.aspx.
The SMS score allows the enforcement community to identify specific safety problems for fleets, and will be used to continuously monitor on-road performance to determine whether a carrier’s safety performance has improved or if intervention is warranted.
Major Impacts
Tires, along with lights, are the two biggest issues facing fleets, based on the real-world results generated since CSA began.
Tires have a major impact on a fleet’s SMS Score. With 18 or more tires on most Class 8 vehicles, the score can increase very rapidly for tire issues.
Tires fall under the Vehicle Maintenance BASICs category. The violations associated with tires can be found on pages A19 to A20 in the appendix of the aforementioned referenced SMS methodology document.
FMCSA has attached a violation severity number to be used in calculating the SMS score, depending on the specific tire issue. Tires carry either an "8" or a "3" severity rating, depending on the violation.
Violations that carry the "8" severity rating include:
- Flat tire or fabric exposed.
- Ply or belt material exposed.
- Tread and/or sidewall separation.
- Flat tire and/or audible air leak.
- Cut exposing ply and/or belt material.
- Steer tire tread depth less than 4/32 of an inch.
- Drive, trailer or dolly tire tread depth less than 2/32 of an inch.
It is obvious that a walkaround vehicle inspection that includes tires should easily identify these high-severity violations. Tires which show cuts and exposed steel or fabric are not recommended to be running on your vehicles.
Tread Depth
Tires with tread depths below 4/32 of an inch for a steer tire and 2/32 of an inch for all other wheel positions have been in effect for just about forever. A simple tread depth gauge will identify low tread depth tires.
Since trailer tires tend to develop more irregular wear compared to tires on other wheel positions, the issue becomes where to measure the tread depth. This is not always obvious.
Highway inspectors need to understand that many tire designs have stone ejectors built into the bottom of the tread grooves. If the tread measurement hits a stone ejector, the measurement can be off 2/32 of an inch.
Air Leaks
A tire with an audible air leak must have a large puncture and this will lead to an eventual tire failure. Just looking at a tire on a vehicle will not determine if a tire is "flat." The tire should be measured with a calibrated tire inflation gauge.
The Commercial Vehicle Safety Alliance (CVSA) considers a tire flat when the measured air pressure is less than 50 percent of the maximum tire pressure molded into the tire sidewall.
The current industry standard followed by most fleets in considering when a tire is flat and needs to be removed is 20 percent below the fleet air pressure specification.
Pressure Gauges
Accuracy of tire air pressure gauges is a big problem. Even brand new "stick" gauges right out of the box are only accurate to +/- 3 psi. A tire with 100 psi actual could be measured as 97 psi with one gauge and 103 psi with a second gauge.
As stick gauges age, the accuracy continues to drop dramatically. The inexpensive spring inside these gauges changes its stiffness properties over a combination of time and dropping the gauge onto hard surfaces.
We have seen gauges that are 20 psi off.
Tire Conditions
The violations that carry a "3" severity rating include:
- Tire underinflated based on load.
- Regrooved tire on the steer axle.
- Weight exceeds tire load limit.
Regrooved tires are primarily used by bus fleets and are not an issue for trucking fleets.
Exceeding a tire load capacity is never suggested for tires, and is clearly illegal.
Tire Underinflation
The one violation on the aforementioned list that can, and probably will, affect many fleet SMS scores is tire underinflation. Every industry study shows that tire underinflation is a widespread issue, especially on inside duals and trailer tires.
The dilemma here is that nobody has clearly delineated a definition of underinflation. Is it 10 percent, 15 percent, 20 percent or even higher?
Is underinflation based on what is written on the tire sidewall or is it based on the fleet’s tire air pressure specification?
Because of the ambiguity surrounding how underinflation is determined, a fleet could rack up violation points fairly quickly as enforcement officers use their criteria to determine that tires on an 18-wheel rig are underinflated, assigning three points for each one that is.
CSA Scoring
The official CSA "score" is quite involved when it comes to tires. Basically, here is how it works.
- SCA assigns weights to time and severity of violations based on a relationship to a crash risk:
+ Last 6 months = 3 x weight.
+ 6 to 12 months = 2 x weight.
+ 12 to 24 months = 1 x weight.
- BASICs violations are ranked on scale of 1 to 10 - with 10 being the worst, and weighted by severity - i.e., relationship to a crash.
- Four BASICs have two additional points added: Fatigued Driving (Hours-of-Service), Driver Fitness, Vehicle Maintenance and Cargo-Related.
Scoring example 1: Underinflated tire and less than 6 months since the last incident.
3 points for underinflation + 2 points for the Vehicle Maintenance BASIC = 5 subtotal x 3 for the time weight multiplier = 15 total tire violation score.
Scoring example 2: Flat tire and 6 to 12 months since last incident.
8 points for a flat tire + 2 points for the Vehicle Maintenance BASIC = 10 subtotal x 2 for the time weight multiplier = 20 total tire violation score.
Not Clear
It is very clear that the point total associated with underinflated, flat and low tread depth tires can quickly add up.
Drivers will not want to be associated with fleets that do not have a serious tire program because points are assessed to both fleets and the individual drivers.
To summarize the CSA program as it relates to tires is very easy: It is clearly not totally clear.
- The definition of an underinflated tire is an unknown.
- There is no consensus on when a tire is really considered flat. Is it 80 percent under fleet specification or 50 percent of the maximum pressure of what is written on tire sidewall?
- Inspectors need to be trained on accuracy of pressure gauges and tread depth gauges, where to measure tread depths and gauge calibration.
