THE increase in armed robberies and illegal road racing is likely to push maintenance costs for police vehicles up by more than 20 per cent. This has put the force in a contrasting situation to other government departments which are saving money on repair costs. An estimated $16.6 million would have been overspent by the police by end of this financial year, according to deputy maintenance service director, Mr John Brian Gouldsmith. In the Legislative Council's Finance Committee meeting yesterday, Mr Gouldsmith failed to convince councillors to approve extra funding of $11.6 million after the force has targeted to save $5 million from its departmental expenses to help foot the bill. Describing Mr Gouldsmith's explanation as ''unconvincing'', legislators demanded a more detailed report before giving the go-ahead. Dismissing charges that the police are using their vehicles in an unreasonable manner, Mr Gouldsmith said the accident rate was actually dropping. He attributed the high repair cost to severe weather conditions and the damage caused by robbers' crossfire. He was defended by Mr Brian Dagnall, development manager of the Electrical and Mechanical Services Department (EMSD) which is responsible for making the budget for vehicle maintenance of different government departments. Mr Dagnall said EMSD should be held partly responsible for the overspending for the inaccurate estimation it made last April.