Anyone who has ever been forced to overpay on a bus fare because of an exact-money-only rule may have wondered how much extra revenue such a policy generates for the bus companies.

Now we have some idea. Figures obtained by The Herald under freedom of information legislation show Lothian Buses made £194,035 above the value of ticket sales in 2012. That amounts to £500 overpaid by passengers every day.

Lothian Buses claims this discrepancy between fares collected and tickets sold is not always caused by overpayments - the ticket machine may not be working in some cases, for example - but it is clear there is a large problem with overpayments on routes which use exact fares only, one which appears to be making a big profit for bus companies.

On the face of it, passengers having to overpay in this way may not seem like a significant problem. For a start, the individual amounts involved are likely to be relatively small, although passengers on tight budgets are more likely to use buses. Lothian Buses has also pointed out passengers can reclaim overpayments at its offices.

However, quite apart from the time-consuming impracticality of reclaiming overpayments, focusing on the relatively small amounts individual passengers have to overpay misses the bigger picture. For some years now, the bus network in Scotland has been under considerable pressure and in some areas there has been a steep drop in the number of people who are within easy walking distance of a bus stop with a frequent service.

If that is to change and the bus network made more accessible and user-friendly, investment will be needed, but new customers will also have to be attracted to the network. In order to do that, the bus companies need to make their service as practical and as easy as possible and the exact-fare policy does not help. Who is going to regularly take a bus if they are faced with a choice between memorising every fare, carrying round pocketfuls of change to cover every eventuality or overpaying?

As the MSP Patrick Harvie says in The Herald today, such a system runs counter to a modern public transport system and change is required. The obvious solution is a smartcard like the Oyster card in London but, as Mr Harvie says, Scotland has been slow in moving towards the introduction of such cards. The benefits of using them are obvious. It would solve the exact-fare problem at a stroke, but if it was properly integrated with the train and underground network, it would also allow passengers to travel across the country on one card. The Oystercard has already demonstrated such a policy can boost passenger numbers.

Some progress has been made on introducing smartcards in Scotland - Glasgow Subway phased them in this year, but the prospect of using them across different types of transport remains distant. Part of the problem has been resistance from the bus operators but they have to realise, first, that their service needs to be as up-to-date and efficient as possible and, second, an exact-fare policy has no place in such a modern, user-friendly service.