Two Bus Éireann drivers have told the jury in the Dublin Bus crash trial that they experienced power surges on a bus in Waterford in 2004 and 2005.
A technical expert for the defence also gave evidence on day seven of the trial that, from data produced by the prosecution, the engine on Kenneth Henvey's bus was generating excess power for 43 per cent of its operating hours.
Mr Henvey (51), of Whitethorn Crescent, Palmerstown, has denied dangerous driving causing the deaths of two men and three women at Wellington Quay on February 21st, 2004.
Bus driver Martin O'Callaghan said he was driving a single-decker Volvo bus in Waterford in May 2004 when his bus "got a power surge, the revs went into the red" and he heard a "large roar".
Mr O'Callaghan, the first witness for the defence, told Patrick Gageby SC (with David Burke) that he had pulled up at a bus stop in Tramore with the bus in gear and the handbrake on when the surge happened.
He put the vehicle into neutral and "got a larger roar" which he described as a "frightening sound".
He turned the engine off, told his passengers to get off the bus and reported the incident to his inspector. He filled in a vehicle defect sheet at the garage and never drove the bus again.
Another Bus Éireann driver, Mark Fitzgerald, told the jury that in June 2005 he was standing on the steps of the same bus in a Waterford garage. He said it was idling when the "revs shot up" and there was an "unnatural roar".
He said a duty inspector filled out an incident report and Mr Fitzgerald wrote to the area manager to inform him of what had happened.
Thomas O'Connell SC (with Patrick McGrath BL), prosecuting, was given permission by Judge Michael White to delay his cross-examination of the two witnesses.
Mr O'Connell also asked for time to consider highly technical evidence from the defence and Judge White told the jury to return tomorrow in order to give the prosecution time to consider those issues.
The defence team's expert, Dr Dennis Woods, said he was a chartered and automotive engineer involved in the investigation of road accidents and had examined data from Dublin Bus and Volvo in this case.
Dr Woods described a power surge as a delivery of extra fuel to the engine. He said that in order for a power surge to happen the fuel pump and fuel injection system must have the capacity to deliver excess fuel and there must be a mechanism within the system to cause such a delivery.
He said an "intermittent fault" in the electronic components of a bus or within the sensors or the fuel pump could result in excess fuel being delivered to the engine.
His tests on a similar engine to that of Mr Henvey's bus revealed that when electrical currents of 2.9 volts and 4.82 volts were applied to the fuel pump it could deliver between 2.5 times and 6.4 times the amount of fuel required for the engine to run at the manufacturer's maximum specifications.
Dr Woods analysed prosecution data downloaded from a computerised recording device on the bus and said it showed "engine speed surges" occurred for over 26 minutes of its operating hours.
The data showed that the engine generated excess power for 43 per cent of its operating hours and delivered up to 2.33 times the specified torque.
Dr Woods told the jury that Garda tests showing times the bus took to cover the distance Mr Henvey's bus travelled were average times and in reality the actual times would be lower.
Dr Woods said he discovered that following Garda tests on the bus in March 2004 it had not been stored in accordance with the manufacturer's instructions. He had therefore not run performance tests on the bus.
The hearing is scheduled to continue tomorrow before Judge White and a jury of four women and eight men.