Guide

The clock a dispatcher is actually planning against

Three numbers decide whether a run can be made in a day: eleven hours of driving, a fourteen-hour window that does not stop for anything, and a thirty-minute break after eight hours behind the wheel. The second one is where most plans quietly break.

US FMCSA property-carrying rules
Two worked timelines
Assessed August 2026

The rules

Three numbers, and one of them behaves differently from the other two

If you already know the rules, skip to the timelines. If you half-know them, this is the half that costs money.

Driving limit

11 hours

maximum driving time after 10 consecutive hours off duty

Duty window

14 hours

measured from coming on duty, and it does not pause

Required break

30 minutes

after 8 cumulative hours of driving time

Reset

10 hours

consecutive off-duty time before a new window opens

The 11-hour driving limit

A property-carrying driver may drive for up to 11 hours after coming off 10 consecutive hours off duty. This is the number everybody knows, and it is rarely the one that binds. Driving is the activity a plan is built around, so it tends to get counted carefully.

The 14-hour duty window

From the moment a driver comes on duty, a 14-hour window opens, and driving is not permitted after it closes. The window is measured on the wall clock. It does not stop for a break, a meal, a fuel stop, a two-hour wait at a receiver, a load that was not ready, a mechanical, or an afternoon spent on a dock. Every minute that passes after the driver comes on duty is a minute gone from the window, whether the truck moved or not.

This is the rule that breaks plans, because it is the rule that turns somebody else's delay into your driver's problem. A dispatcher planning an eleven-hour driving day inside a fourteen-hour window has three hours of slack to cover loading, unloading, the break, fuelling, scaling and traffic. Three hours is not much, and detention eats it first.

The 30-minute break

A driver may not drive after 8 cumulative hours of driving time without taking at least 30 consecutive minutes of non-driving time. The break can be off duty, in the sleeper berth, or on duty not driving, so time spent on a dock can satisfy it. What it cannot do is stop the 14-hour clock. The break is time you have to spend and time you do not get back.

Note that the trigger is cumulative driving hours, not elapsed hours. A driver who has been on duty ten hours but has only driven six of them has not triggered it.

Fourteen hours from the moment the driver comes on duty. The window is measured on the wall clock, and nothing stops it.

FMCSA hours of service for property-carrying drivers, 49 CFR 395

The fourteen-hour window draining across a full driving day

Hours left in the window at the end of each activity on the clean day set out below. It falls at the same rate whether the truck is moving or not, and the day finishes with 30 min of it left.

The single most expensive misunderstanding

Planning software that treats the 14-hour window as pausable will produce a plan the logging device rejects. If your tool tells you a driver can absorb a three-hour detention and still make an eleven-hour driving day, it is not modelling the window. There are only 14 hours, and everything that is not driving comes out of the same 14.

Timeline one

A clean day, hour by hour

On duty at 06:00, so the window closes at 20:00. Nothing goes wrong. This is what a full driving day looks like when it works.

A compliant fourteen-hour duty day with eleven hours of driving.
Time	Activity	Driving used	Window left
06:00 – 07:00	Pre-trip inspection and loadingOn duty, not driving. The window has started.	0 min	13 h
07:00 – 11:00	Drive	4 h	9 h
11:00 – 11:30	Fuel and the 30-minute breakTaken at 4 hours of driving, well inside the 8-hour trigger.	4 h	8 h 30 min
11:30 – 15:30	Drive	8 h	4 h 30 min
15:30 – 16:30	Unload at the first consignee	8 h	3 h 30 min
16:30 – 19:30	DriveThis brings driving to the 11-hour limit.	11 h	30 min

Driving used reaches 11 h, which is the limit. The window closes at 20:00 with 30 min to spare. Total time on duty and driving: 13 h 30 min.

Read the last column. The whole day finishes with 30 min of window remaining. That is the entire buffer: half an hour, for the whole day, against traffic, weather, a scale queue, a receiver who is not ready and a dock that is short a forklift driver.

A plan that uses all 11 driving hours is not a plan with slack in it. It is a plan that works if nothing at all goes wrong, and something usually does.

A plan that uses all eleven driving hours is not a plan with slack in it. It is a plan that works only if nothing goes wrong.

Timeline two

The same day, with three hours of detention

Same driver, same start time, same route. The shipper is three hours late releasing the load. Nothing else changes.

The same duty day after three hours of detention at the shipper.
Time	Activity	Driving used	Window left
06:00 – 09:00	Pre-trip, then waiting at the shipperThree hours of detention. No driving, and the window runs anyway.	0 min	11 h
09:00 – 13:30	Drive	4 h 30 min	6 h 30 min
13:30 – 14:00	The 30-minute break	4 h 30 min	6 h
14:00 – 17:30	DriveDriving now stands at 8 hours.	8 h	2 h 30 min
17:30 – 20:00	DriveThe window closes here, with driving hours still unused.	10 h 30 min	0 min

Driving used stops at 10 h 30 min because the window closed at 20:00, not because the driver ran out of driving hours. 30 min of legal driving time went unused.

What the detention actually cost

Three hours of waiting did not cost three hours of driving. It cost 30 min, because the day was already going to finish with 30 min of window unused, and the unloading stop had to be dropped from the plan to fit. At 55 mph that is roughly 28 miles that the load does not travel today.

The important part is that the driver still has 30 min of perfectly legal driving time left and is not permitted to use any of it. The window is closed. The only lawful next move is 10 consecutive hours off duty, which puts the delivery into tomorrow.

Why this is a planning problem, not a driver problem

Nothing in either timeline is the driver's doing. The difference between a delivery made today and a delivery made tomorrow was decided by a shipper's dock at 06:00, and it became visible at 20:00. A dispatcher who can see the window closing at 09:00 has options: re-sequence the stops, hand the load to a relay, or tell the receiver now rather than at seven in the evening. A dispatcher who finds out at 20:00 has none.

Where the detained day's fourteen hours went

21%

75%

On duty, not driving3 h
Driving10.5 h
The 30-minute break0.5 h

The same 14 hours as the clean day, divided differently. 3 h of it went on the pre-trip and then on waiting for a load to be released, and that is the reason driving stopped at 10 h 30 min rather than 11 h.

Planning

How to plan a run against this clock

The rules are simple. Planning against them is a discipline, and it comes down to five habits.

01
Plan the window first, then the driving
Start from the moment the driver comes on duty and mark the close of the window on the plan before anything else goes on it. Everything else has to fit inside that mark. Planning the driving first and then discovering the window is the standard way to build a plan that cannot be logged.
02
Budget every non-driving minute explicitly
Loading, unloading, fuelling, scaling, the pre-trip and post-trip inspections, and the 30-minute break all come out of the same 14 hours. In the clean timeline above they add up to 2 hours 30 minutes. If your plan does not have a line for each of them, it has an optimistic total.
03
Place the 30-minute break where it does useful work
The break has to happen before 8 cumulative driving hours, and it may be taken as on-duty non-driving time. Placing it at a fuel stop, a scale, or a dock that was going to take half an hour anyway makes it free. Placing it in the middle of a clean run makes it cost 30 minutes of window.
04
Treat detention as a live input, not an exception
A dispatcher who knows at 09:00 that the driver is still on the shipper's dock knows the delivery is not happening today, and can say so while it is still a phone call rather than a failure. This only works if the clock is being tracked against the plan during the day rather than reconciled after it.
05
Re-check the axle weights at every point on the timeline
The clock is not the only thing that changes during a run. Fuel burns off the steer axle and the drive tandem, and freight comes off at each drop. A load that is legal at the pump can be over on the steer axle four hundred miles later, and the weigh station on that corridor arrives at a specific time that the timeline already knows.

The edges

The rules around the three rules

Five provisions that change what a plan is allowed to do, in roughly the order a planner runs into them.

The 10-hour reset

A new 11-hour driving allowance and a new 14-hour window both require 10 consecutive hours off duty first. This is why a run that overruns by thirty minutes can cost a great deal more than thirty minutes: the next window cannot open until ten hours after the driver stops.

The 60 and 70-hour limits

Beyond the daily rules there is a weekly one. A driver may not drive after 60 hours on duty in 7 consecutive days, or 70 hours in 8 consecutive days, depending on whether the carrier operates every day of the week. On-duty time counts here, not just driving time, so a week of heavy detention can put a driver out of hours without many miles behind it.

The 34-hour restart

The weekly limit can be reset by taking 34 or more consecutive hours off duty. Planners use this deliberately: a restart placed over a weekend buys a full weekly allowance for Monday, and a restart placed badly wastes two days.

The sleeper berth split

The 10 hours off may be taken in two parts. One part must be at least 7 consecutive hours in the sleeper berth; the other must be at least 2 consecutive hours off duty or in the sleeper berth, and the two together must total at least 10. Neither of the qualifying periods counts against the 14-hour window. That last clause is the whole value of the provision: used properly, a split lets a driver park out an afternoon of traffic or a dock delay without spending the window on it.

Adverse driving conditions

Conditions a driver could not have known about at dispatch may make a run take longer. Weather and an unexpected closure are examples. In those cases, both the 11-hour driving limit and the 14-hour window may be extended by up to 2 hours. It is a genuine provision and it is not a general-purpose extension. Congestion the dispatcher could have anticipated does not qualify.

The short-haul exception

Drivers operating within a 150 air-mile radius of the normal work reporting location, and returning to it within 14 hours, are exempt from some of the logging requirements. Local and regional work often runs under this provision, and a planner moving a driver between local and over-the-road work needs to know which set of rules that driver's day is being logged under.

Somebody else's dock at six in the morning decided whether this delivery happened today. It became visible at eight in the evening.

Scope, and the date on it

These are the United States FMCSA rules for property-carrying drivers, assessed from publicly published documentation as of August 2026. Passenger-carrying rules differ. Canadian and European driving rules are different regimes with different numbers, and a run that crosses into one of them is subject to that regime rather than this one. Nothing here is legal advice; it is the arithmetic a planner has to do.

Put the planning-hours guide against one real load.

Bring the route, configuration or scale ticket that made the planning-hours guide matter. We will work through it in plain English and show where AxleGuard changes the decision.

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