What does a fixed 30-minute travel gap cost a year?

What this model measures, and who it is for

A fixed gap is one number of minutes held between every pair of bookings, whatever the next address. Booking tools call it a buffer, blocked time or a travel gap. This model asks what that number costs over a working year, both ways: minutes held but not needed, and minutes needed but not held.

It is for a solo mobile or home-visit business that already uses a fixed gap. It tells you less if you do one or two long jobs a day, or if your diary has plenty of empty time anyway, because idle minutes only cost bookings when customers want them. To choose the gap itself, use the travel buffer guide.

• Work out the gap you need from your own journeys

Method and assumptions

Every figure comes from one small calculation, with inputs chosen to be easy to follow. They are modelled scenarios, not CalMov customer data, and none of the four gaps is presented as typical.

• 5 visits a day, so 4 changeovers. Drives from base and back home are left out: a gap between bookings doesn't cover them.
• 230 working days: about 260 weekdays, less the 28 days' paid leave GOV.UK says most workers on a five-day week must get (bank holidays can count towards it), rounded down from 232 for illness or vehicle trouble. Self-employed people get no holiday pay, so use the days you plan to work.
• Real changeover: from finishing one service to being ready to start the next, so pack-down, the drive, parking, getting in and setup. A mapped drive time is only part of it.
• 60-minute visits that finish on time, and an illustrative £40 a visit, which is not a suggested or typical price.
• No safety margin: an exact fit means no spare minute.
• Hours are rounded to the nearest hour and extra visits down to whole visits.

need = the real changeover, in minutes
late = how late you are running (0 at first visit)
max(0, x) = x, or 0 if x is below 0

For each changeover, in order:
  idle += max(0, gap - need - late)
  late  = max(0, late + need - gap)

Idle hours a year
  = idle minutes a day × 230 ÷ 60
Extra visits, at most
  = idle minutes a year ÷ (60 + need)
Takings, at most = extra visits × £40

Scenario 1: every changeover takes the same time

Here all four changeovers in a day take the same time. Read across a row for the gap you set, and down a column for how long your changeovers really take.

Idle time depends only on the surplus: 4 changeovers × 230 days ÷ 60 is about 15.3 hours a year per surplus minute, so 10 minutes costs 153 hours, nearly four 40-hour weeks. A shortfall compounds instead: the second visit starts late by the shortfall, and the fifth by four times it.

What the idle hours could hold

Idle minutes become a booking only when a whole visit and the journey to it fit inside them. Divide the idle minutes a year by a visit plus its changeover for the most extra visits they could hold.

That ceiling assumes minutes can be pooled, but they arrive a few at a time, on different days. The last column is the stricter test: on a full five-visit day, would the minutes the gap wastes fit another visit? With a 30-minute gap and 20-minute changeovers, the day frees 40 minutes and another visit with its journey needs 80, so the cost is a later finish, not a lost booking. If customers want the time, your figure falls between the two.

When the gap is too short, lateness adds up

A gap shorter than the changeover costs no idle time. It costs punctuality, and the delay carries forward: each short changeover adds to it, and only a later one with time to spare takes it away.

With a 30-minute gap on 45-minute changeovers, the second visit starts 15 minutes late, the third 30, the fourth 45 and the fifth an hour late: two and a half hours of customers waiting, and a finish an hour later than planned. That is four late starts a day, or 920 over 230 days.

Skipping a break or rushing setup wins some back, at a cost the diary doesn't show.

Scenario 2: a day where changeovers vary

Here the four changeovers take 15, 30, 10 and 25 minutes, in that order. The average is 20 minutes, as in the middle column of scenario 1, so any difference comes from the variation alone.

A gap set to the average still makes two visits a day late, because you only catch up when a short changeover follows a long one; in the reverse order, it makes three late. The smallest gap that is never late is 30 minutes, the longest changeover, and it holds back 40 minutes a day. Over 230 days that is 153 hours: the price of covering every journey with one number.

Real drive times vary, and a map shows only the drive

The scenarios treat each changeover as known, but real drives change with the route and the time of day. The Department for Transport's report on local 'A' roads in Great Britain for April 2025 to March 2026 gives average weekday speeds of 23.3 mph from 7am to 10am, 23.9 mph from 10am to 4pm, 22.1 mph from 4pm to 7pm and 29.7 mph from 7pm to 7am, with the lowest speeds generally in the two peaks. Urban 'A' roads averaged 17.6 mph; rural ones, 34.4 mph.

Those are national averages; only your own records show how much your routes vary. And a mapped drive time covers the drive alone. Parking, walking to the door, getting in, setup and pack-down are not in it, and they change from address to address. Count each once, in the changeover or in the service length.

What a per-journey travel time does instead

A per-journey travel time works out each journey from the two addresses involved, instead of giving every journey the same number. In scenario 2 it would hold 15, 30, 10 and 25 minutes, so the allowances leave no idle minutes and cause no late starts. It is still an estimate, so keep a margin, and it does not plan or reorder your route.

In CalMov, the customer enters their address first, and CalMov only offers times you can actually reach, allowing for the journey before and after each visit. On Lite, which is free, the allowance is a fixed travel gap between bookings that you set, so this model applies to it directly. On Pro, CalMov uses road-based drive times with expected traffic. The calendar shows the drive time between visits, and dragging a booking checks that the new time fits, including the drive.

A fixed gap costs little when your changeovers are within a few minutes of each other. If your worksheet shows otherwise, compare the plans.

• Compare Lite and Pro on the pricing page
• Read the CalMov Lite vs Pro comparison

Do it with your own numbers

You need a normal working week of records and a spreadsheet or notepad, with one row per changeover.

• Write down your current fixed gap in minutes.
• For a week, time each changeover from the end of a service to being ready to start the next, noting the mapped drive apart from pack-down, parking, access and setup.
• Count your changeovers a day (visits minus one) and your working days a year.
• Run the two lines of the calculation for each day, in order, starting with late at 0. Total the idle minutes; note each late start.
• Idle hours a year = average idle minutes a day × working days ÷ 60.
• For a ceiling on bookings, divide idle minutes a year by visit length plus your usual changeover; multiply by your price.
• Repeat with the gap set to your longest regular changeover. Its idle hours are what never running late costs with one number.
• If both results are small, your gap is fine. If either is large, try per-journey times or grouping customers by area.

• Work out what an hour of a booking earns
• Ways to group customers and reduce travel gaps

Limitations

• These are modelled scenarios, not observations. No CalMov customer data was used.
• Every visit lasts 60 minutes and ends on time; real services run over or finish early.
• Only journeys between customers count, and each is treated as known; on the day, traffic, parking and access move it.
• Lateness is only made up by later spare minutes, never by rushing or skipping a break.
• Idle time isn't automatically lost: it may hold a break, admin or a phone call.
• Takings are before costs, and the ceilings assume every freed slot is booked.
• The 230 days and £40 are assumptions to replace with your own.