The Federal Motor Carrier Safety Association’s (FMCSA’s) Hours of Service (HOS) rules have a reputation for complexity. It’s true they can be confusing, with multiple overlapping time limits covering a wide variety of situations.

But there’s reason behind the HOS regulatory tangle.

The FMCSA is constantly weighing its central mission—to prevent accidents and injuries involving commercial vehicles—against the operational goals of shippers, drivers, and carriers. To find that narrow overlap between flexibility and safety, regulators often conduct studies, using real-world data. That sometimes leads to figures that can leave drivers scratching their heads.

The 34-hour reset rule is a case in point. Why 34 hours? Why not 24 or 48 hours, time spans that correspond more closely to the way we organize our weeks outside the trucking industry? The answer is in the data:

The FMCSA’s studies suggest that 34 hours is the minimum time it takes to meaningfully reduce driver exhaustion after long working weeks. Any more, and they’d further complicate driver scheduling. Any less, and they may allow more exhausted drivers onto the road.

But that still leaves a lot of questions about the 34-hour reset rule, and the language of the HOS regulations (49 CFR 395) isn’t always easy to understand. Here are answers to a few frequently asked questions about the 34-hour reset rule for truck drivers. Consider it a helpful scheduling tool for working within HOS rules.

A Simple 34-Hour Reset FAQ

What is the 34-hour reset rule, exactly?

What we typically call the “34-hour reset rule” is really just a subclause in the broader FMCSA HOS regulations. Noting that fatigue is cumulative, regulators place limits on how long a commercial truck driver can drive within both daily and weekly time periods.

Those limits include:

Hours Of Service Limits For Truck Drivers

• 11 total hours of driving per shift
• No driving after the 14th consecutive hour of the shift (which includes both driving and non-driving activities)
• At least 10 hours of off-duty time between shifts
• Required 30-minute breaks after eight hours of cumulative driving
• 60 hours of driving within each seven-day period, or 70 hours of driving within each eight-day period

Pay attention to those last two, which we’ll call “weekly limits,” even though they don’t refer to a traditional Monday-through-Friday working week. A 34-hour reset is what restarts that weekly clock. For truck drivers, each “work week” may consist of either seven or eight consecutive days on duty. Because these work weeks aren’t tied to the calendar, drivers need a way to end one multi-day work period and begin the next. According to the FMCSA, 34 hours off duty restarts the work week; it allows the full 60 or 70 hours of driving to begin from scratch.

How often do drivers have to take 34 hours of time off?

The most surprising thing about the 34-hour reset rule is that it isn’t mandatory. Many drivers take it without really being aware; if you have a set route, and you’re home every weekend, you take a 34-hour reset incidentally. You just call it your weekend.

Here’s another odd fact: As long as drivers take 10 hours off between shifts, they could conceivably drive up to 8 hours and 45 minutes per day, every day, without violating HOS regulations. Here’s how we came up with that figure:

In other words, as long as you’re driving less than 8 hours and 45 minutes per day, you’ll never reach the 70-hour limit within any given eight-day consecutive period.

Of course, the fact that the regulations would allow such a schedule doesn’t mean it’s a good idea. If you’re a fleet owner, you’ll have happier drivers when you offer regular weekends (or at least consecutive days) off. So within most driver schedules, the 34-hour reset operates in the background, without drivers having to make any sort of official declaration.

When should drivers take a 34-hour reset? In other words: What’s it good for?

Imagine a scenario in which you know you’ll need to drive 50 hours between Monday and Friday, and another 22 hours by the following Monday. If you only took the mandated 10-hour breaks between shifts, your clock would go over the 70-hour limit sometime over the weekend—an HOS violation.

Instead, you could take a 34-hour off-duty period from 6 p.m. Friday to 6 a.m. Sunday. Your clock would reset at zero; you’d be starting another eight-day working week that Sunday. You could get your final 22 hours of driving on Sunday and Monday, something that would have been impossible without the break—at least while complying with HOS regulations. That’s the sort of situation in which the 34-hour reset can be helpful. It’s a tool drivers use to restart the clock, for those times when you must distribute your 60 or 70 hours of weekly drive time creatively.

How do drivers log their 34-hour off-duty periods?

If you’re wondering how to do a 34-hour restart, we’ve got good news; it’s simple, thanks to electronic logging devices (ELDs).

These ELDs are required for all commercial vehicles, and they make it easy to log off-duty time. A driver embarking on a 34-hour break just needs to set the ELD to off-duty (or “sleeper berth” if they’re taking time off in a sleeper cab). The ELD’s clock will keep running; the software will know when 34 hours is up. If you’ve maxed out your driving hours and try to go back on duty before that 34-hour period is over, the ELD will warn you about the potential violation. It’s as simple as that, and another example of the ELD rule making life a little easier for drivers.

What happens if a driver violates the 34-hour reset rule?

If your clock goes over 60 hours in a seven-day period, or 70 hours across eight days, you’ve violated HOS rules. The ELD will record the violation and file it away in the FMCSA’s Safety Measurement System (SMS). Hours of Service violations are just one of the seven factors that the SMS measures as part of its goal to track carrier safety, but they contribute to your organization’s Compliance, Safety, and Accountability (CSA) score, a percentile figure in which the lower your score, the better.

High CSA scores can result in FMCSA interventions, from compliance reviews to out-of-service orders, which revoke a carrier’s permission to conduct interstate commerce. Your CSA score also affects insurance rates and can lead to insurers refusing coverage, which is an existential threat to your business. In short, it’s best to avoid HOS violations entirely—and that includes compliance with the 34-hour reset rule.

Where can I learn more about HOS regulations?

The FMCSA offers lots of resources to help fleet owners and truck drivers navigate HOS rules. Here are just a few:

• FMCSA HOS Home Page
• FMCSA HOS FAQ
• FMCSA’s Educational Tool for Hours of Service (ETHOS)

To learn more about compliance and other trucking-industry concerns, keep an eye on the Bobtail blog. As creators of a factoring tool built by truckers, for truckers, we’re always sharing resources that can help your business grow.

And if you’re looking for a new type of factoring service—one without contracts, hidden fees, or volume requirements—sign up to learn more about Bobtail today.