I ran a twelve-vehicle fleet for two years on a shared Google Sheets rota. Column A: driver name. Column B: days available. Column C: notes. It worked. Nobody missed a shift. We always knew who to ring on a Wednesday morning.
What it couldn't do — what no general-purpose calendar tool was ever built to do — is tell me whether the driver who said they were free on Wednesday was legally available to drive that Wednesday. And that distinction, which sounds like a pedantic compliance detail, cost me a pointed conversation with a DVSA traffic examiner at Stafford Services northbound and a very uncomfortable hour explaining what our driver monitoring system looked like.
It looked like a Google Sheets spreadsheet. The examiner was not impressed.
The gap between free and legally available
For a warehouse picker or a parcel courier, "available to work Wednesday" is a simple question. Are you free? Yes? Booked. For an HGV driver, the question is more complicated — and the complication has legal weight behind it.
A driver can be physically available — rested, willing, at the yard — and still not legally deployable on a given day. Not because they're unfit to drive. Because their 144-hour weekly rest window is closing that afternoon, or their WTD reference period average is about to tip, or their driver card download is overdue and sending them on a week-long run would mean the data gets overwritten somewhere between Immingham and Carlisle.
None of those things show up in a shared calendar. All three of them are the operator's problem as much as the driver's.
Three compliance windows that eat into deployability
There are three areas where a driver's legal position directly affects whether they can take a shift. Most fleet managers have a rough handle on the first one. The second and third tend to disappear into the noise of running day-to-day operations.
The 144-hour weekly rest window
Under EU Regulation 561/2006, retained in UK law, a driver must begin their next weekly rest no more than 144 hours — six days — after the end of the previous one. Miss that window and you're looking at a very serious infringement for both driver and operator. Not a minor breach. The category that ends careers and OCRS scores in the same meeting.
In a tidy Monday-to-Friday operation, tracking this is easy. But agency drivers working across different operators, tramping runs that end mid-week, and handover arrangements between companies mean the start and end points drift all over the calendar. A driver whose last weekly rest ended on a Tuesday at 07:00 has until Monday at 07:00 the following week to begin the next one. Book them on a Sunday evening long-distance job that finishes Monday afternoon and you've already blown the window before they've even loaded the trailer.
The rota shows them as available. The 144-hour window says otherwise. Without the compliance layer, you don't know until something goes wrong.
The WTD 17-week reference period
The Road Transport (Working Time) Regulations 2005 apply to employed mobile workers — the majority of drivers in most small fleets. The 48-hour average is calculated over a rolling 17-week reference period. A driver can work 60 hours in a single week without a breach. But the 17-week rolling average must stay under 48 hours.
The practical trap: six weeks of heavy shifts — say, 55 hours a week — followed by a period where you're short-staffed and using the same driver every available day. By the time the average tips over 48, you're three or four weeks past the point where the problem was fixable. You can't wind it back. You can only wait it out, which means taking that driver off the road for the weeks needed to bring the average back down.
I covered the 17-week maths in detail in this post on the WTD reference period. The short version: the running average is invisible in a simple rota, and by the time it's visible, the damage is already done. You need to be watching it before it tips, not after.
Driver card download deadlines
The driver card must be downloaded at least every 28 days. The vehicle unit every 90 days. Miss the 28-day window on a card and the data cycles over — you've got an unexplained gap in your records, which DVSA treats as a recording failure, separate from and in addition to any infringement the gap might have contained.
This affects scheduling directly. A driver whose card was last downloaded 22 days ago, who's about to go on a three-week tramping run to Scotland with no download facility at the far end, is not fully deployable in compliance terms. You need a mid-run download at day 25, or the run doesn't work legally. A scheduling tool that doesn't know the download position can't flag that. A spreadsheet definitely can't.
What this looks like in practice
Here's a concrete example. Monday morning. You've got a Stafford–DIRFT–Birmingham triangular run starting Wednesday. Two drivers available Wednesday through Sunday on the rota. Both willing. Both ticked as free.
Driver A: last weekly rest ended Sunday at 07:00. 144-hour window closes Saturday at 07:00. Wednesday start, Saturday finish — tight, but technically inside the window. Except Driver A's WTD running average over the previous 14 weeks is sitting at 49.3 hours. Another full working week pushes the 17-week average to 49.1. That's a breach.
Driver B: last weekly rest ended Monday at 08:00. 144-hour window doesn't close until Sunday morning. WTD average is 44.2 hours over 17 weeks. Card was downloaded Friday. Clean on all three counts.
Without the compliance layer, both look identical on the rota. With it, you pick Driver B and nobody has a problem. The benefit isn't dramatic. It's just the right call, made before the vehicle left the yard instead of three months later in a traffic examiner's meeting room.
Agency coordinators face this problem hardest
At least a fleet manager has all their driver data in one place. Agency coordinators are managing drivers who work for multiple clients across the week — sometimes multiple operators on the same day. The 144-hour window doesn't reset when the client changes. The WTD reference period doesn't care which booking it belongs to. But most agency dispatch systems are built around client relationships, not driver compliance positions.
The result: coordinators running on instinct, memory, and a spreadsheet note someone added two months ago saying "watch his hours." Works until it doesn't. When it doesn't, the liability conversation is complicated — I wrote about how that splits between agency and operator in the agency driver hours liability post. Short version: a coordinator who can show they checked the compliance position before confirming a booking is in a materially different position from one who just said yes and moved on.
Why this is an operator obligation, not just a driver one
I've heard the argument. "The driver knows their own hours. If they accept the work and they're over, that's on them." And there's a kernel of truth — drivers are responsible for their own 561 compliance. A driver who knowingly accepts work past their limits is in the wrong.
But Traffic Commissioners don't accept "the driver knew their position" as a complete defence for the operator. The O-licence conditions specifically include a monitoring undertaking — the operator must have systems in place to detect infringements. A fleet running on a calendar with no hours visibility is not meeting that undertaking. The TC knows what a functioning monitoring system looks like. A Google Sheets rota is not it.
The documentation matters not because it prevents infringements on its own, but because it demonstrates a functioning system. DVSA's test at a roadside encounter or a traffic examiner visit isn't just "did something go wrong" — it's "did you have a system that should have caught it."
What a proper availability tool needs
For the compliance layer to work, the scheduling tool needs to know — per driver, updated as each shift is logged:
- Date and time of last weekly rest completion, and whether it was full (45h+) or reduced (24h+), and whether compensation rest is owed
- Running WTD total for the current reference period and how many weeks are in the window
- Driver card download due date
- Vehicle unit download schedule per vehicle
ShiftOwt connects that compliance data to the availability calendar. When you're slotting a driver into a run, you see their legal position alongside their availability. If there's a problem, it surfaces before you confirm the booking — not after you're already committed.
It's not a tachograph analysis system and it doesn't replace your tacho software. What it does is put the output of that analysis — the hours position — into the scheduling view. So the person filling the rota has the information they need, on the day they need it, without having to open a second system that lives on the TM's laptop and is never open on scheduling day.
If you're still managing driver shifts on a shared calendar with hours tracking handled separately, ShiftOwt is worth ten minutes. It's £5.99/month for individual drivers, fleet and agency pricing on request. The version I wish I'd had before the examiner sat down at Stafford.