It's a car that has been built to withstand bullets and grenade attacks - but US President Barack Obama's limousine, it seems, can't handle bumpy driveways.The low-riding, six-metre-long Cadillac became stuck on a section of ramp while trying to exit the US embassy during the President's tour of Ireland yesterday.The General Motors-built limo, which is nicknamed "The Beast" and weighs several tonnes more than a regular car due to the layers of protective shielding built into its panels, scraped to a halt in front of a crowd of spectators.Video shot by members of the crowd shows the car crunching to a stop, with the crowd collectively gasping as the car bottomed out on the steeply pitched section of driveway.The vehicle was stuck for more than a minute in plain view of the crowd before the President's Secret Service team positioned other vehicles in front of the stranded stretch limo to protect the car, to the disappointment of the crowd.A US Secret Service spokesman told media that the limo that became stuck was the spare presidential limo. The President was in a second limo in the motorcade."A Secret Service spare limousine, carrying staff and support personnel only, bottomed out at the top of the driveway rendering the vehicle inoperable," Robert Novy said."Occupants were relocated into other vehicles and the motorcade departed out another exit without further incident. There were no injuries."The size of our vehicles is always an issue and taken into consideration during the advance process. However, it only takes a slight miscalculation for a problem like this to occur."The incident is an embarrassment for the Secret Service team considering the state of security for the US President's first overseas trip since US forces killed Osama bin Laden.The hand-built Cadillac limo is actually based on a commercial vehicle platform. It reportedly features a number of state-of-the-art safety technologies, including night vision cameras, pump-action shot guns, tear gas cannons, and shred- and puncture-resistant Kevlar-lined tyres.The boot is also used to house fire-fighting equipment and an oxygen cylinder that can feed air into the cabin in the event of a chemical attack.The half-a-million-dollar limousine is powered by a 6.5-litre turbo diesel engine, and reportedly has a 0-100km/h time of 15 seconds.