It is impossible for a driver to carry change not only due to the additional weight in addition to all the gear he/she has to carry to the relief points where drivers change over. Also there is nowhere to store lots of change in the tiny cabs, more especially the newer ones as the space has been reduced for additional passenger space for wheelchairs and prams etc. Remember a bus driver cannot nip into the bank or send a junior member of staff out to get more change. Many bus companies do not supply floats due to the sheer number of buses on the road for example FIRST have around 12500 drivers per day at work, times that by £50 worth of change and you have £625,000 of dead money floating around so any change the driver has is usually out of his own pocket or is because other passengers have not been too lazy to ensure they have the correct change for the bus so that the inconsiderate ones that are too idle to do this can peel off a £20 note for the £1.20 fare. A change voucher is usually offered or other methods of payment (contactless) but of course there are always the ones that want to make a point and make a fuss usually by abusing the drivers in the most appalling way which is really the reason they are kicked off the buss, but there are no free rides so it is pay or get off. It is true there is no legal requirement to give change in any business. As far as the vulnerable and children travelling they should never be refused travel due to a lack of funds, however, trying to con the driver, sneak on to the bus or use another's pass is a no no, which will end up with the refusal of travel due to fraud /anti social behaviour. A child should approach the driver and advise that they have insufficient funds though this will not wash if they have just come out of the sweetshop having spent their fare or are trying it on repeatedly, just some of the reasons for refusal of travel that get omitted when reported in the press. But the right of travel for vulnerables exists for obvious reasons, as stated refusal is usually because the little angels are actually little devils.