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Carpool Rota Generator

The rota on the fridge is a list of names in a circle, and it survives until the first week somebody is away. Then a turn is either skipped or handed to whoever happens to be standing there, and by the end of term one person has driven twice as often as everyone else. This works the turns out from who is actually travelling on each journey and how big each car is, shares them in proportion to how often each person comes along, and keeps the same person off two journeys in a row where it can.

What this generator does

Works out how many are travelling on each journey, rules out anybody whose car is too small for that load, shares the turns in proportion to how often each person travels, and then matches journeys to drivers — backing a journey out onto somebody else where that is what it takes to fit.

How to use this tool

  1. List the journeys — days of the week, dates, or separate outward and return runs.
  2. List who travels, how many passengers their car seats, and which journeys they are on.
  3. Work out the rota and read who drives when.
  4. Check the turns against the shares underneath, and copy the rota when it looks right.

Understanding the controls

Journeys
Anything you like, in the order they happen. Outward and return runs can be listed separately if they are driven by different people.
Who travels
Name, seats for passengers, and optionally which journeys. Seats do not count the driver, so a car with a driver and four seats takes four other people.
Nobody twice running
A preference, not a promise. It is met by swapping two journeys between drivers, which leaves everybody’s number of turns exactly as it was, and it yields wherever the cars and the shares leave no room.

Common use cases

  • Sharing the school run between four families for a term
  • Setting up a commuting lift share where people work different days
  • Arranging transport to weekly training when only some cars are big enough
  • Splitting the driving on a group trip so nobody does it all
  • Settling an argument about whose turn it is with a rota that shows the arithmetic

How this generator works

Taking the first person with a turn to spare is the rule that strands the last journeys on nobody, because the people who can drive them have already been used up. Instead a journey that finds no free driver pushes one of that driver’s journeys onto somebody else, and so on down the line. The finished rota is then read back: every driver checked against who was travelling, every car against the load, and every total against the shares.

Randomness and fairness

Your browser’s secure generator decides only which of several equally fair rotas you get, and the order swaps are tried in. Working it out again may give a different rota that shares the turns just as evenly.

For how randomness is produced across the whole site, see how Generate Random works.

Limitations and good to know

  • One car per journey. A load that needs two cars is reported rather than split, because who rides with whom is a different question.
  • Up to 40 journeys and 20 people.
  • It knows who travels, not who is willing to drive on a particular day. Somebody who cannot drive at all can be given no seats.
  • The shares are the fairest split of the turns available. Where somebody’s share falls on a journey another person has to take, the rota says the shares could not all be met.

Privacy and your data

Names, cars and journeys stay in your browser. Nothing you type is transmitted, stored or measured.

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