An amphibious bus that can travel on water and roads has been grounded less than an hour after taking to the water.

Trials of the "amfibus" on the River Clyde had to be abandoned because of a technical problem.

Operators Stagecoach were carrying out a two-day test and demonstration of the bus between Renfrew and Yoker.

But the trial was interrupted on the second run when the bus developed a problem with its suspension as it drove up the slipway at Renfrew.

The tests are to continue once engineers have resolved the glitch.

Stagecoach spokesman Steve Stewart said: "We had a couple of trips very smoothly back and forward across the Clyde but when we came back on one of the journeys part of the suspension which involves an airbag popped out, so we are going to have to do some work to put that back in.

"But it's all part of the challenges that you face when you have a technical trial and that will go back into the evaluation process."

Stagecoach had intended to have two hours of tests but had to stop after half an hour.

Based on a bus chassis, the amfibus uses a hull that allows the vehicle to float. While it operates like a normal coach on the road, when it is in water it is driven by twin water jets and can achieve a speed of eight knots.

The £700,000 Dutch-made vehicle can carry 50 passengers and may replace the ferry service between Renfrew and Yoker, which is to be scrapped to save money. The 500-year-old service will stop running in March because operators Strathclyde Partnership for Transport said it needs to save money.