ISIL truck bombs are difficult to stop

AFP:

They're easy to drive and hard to stop, can be made on a farm and destroy a city block: the Islamic State group's monstrous truck bombs are reshaping the battlefield.

IS fighters have used looted armoured personnel carriers, pick-ups, tankers and dump trucks. They pack them with tonnes of explosives and weld steel cages around them.The jihadists used about 30 explosives-rigged vehicles in the Iraqi city of Ramadi this month, blasting their way through positions government and allied fighters had managed to hold for more than a year.

When a position is too well defended for a more conventional advance, a suicide driver steers a truck bomb, protected by the makeshift armour, through enemy fire and straight to his target.

"They are protected from 12.7mm (heavy machinegun) fire and even some RPGs (rocket-propelled grenades). There's so much explosives (inside) that it's still effective at 50 metres (yards)," an Iraq-based military expert said.

Videos of the truck bomb attacks, which IS has also used in the battle of Kobane in northern Syria and on other fronts, show huge explosions that are visible from miles away.

"The damage is bigger than that of a half-tonne bomb dropped by a fighter jet," the Western expert said. "Truck bombs are their air force."
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I think an RPG aimed at the engine of the truck should stop it.  The key would be to set up the defensive position in a place that hit it before it got within range of the target and the troops defending it.  Anti tank weapons would also do the job, if the Iraqis had people who could operate them.
 
Of course, it also takes courage to stand there and fire your weapon at the vehicles with a monstrous blast radius.  That probably explains why many of the Iraqis drove themselves out of Ramadi.