WASHINGTON - The Pentagon plans to deploy billions of dollars in heavily armoured vehicles, spy planes, jamming technology and even experimental ground-penetrating radar to defend troops from increasingly lethal roadside bombs. More than 175 American and allied troops were killed by roadside bombs in Afghanistan last year, more than twice as many as the year before, and American commanders say the 17,000 extra troops ordered to Afghanistan by President Barack Obama last week will offer additional targets, according to The New York Times Thursday. While improvised roadside bombs have been a greater threat in Iraq, the Taliban-led insurgency has begun to use them on a wider scale in Afghanistan, the report said. Military officers say Afghanistan's topography and primitive infrastructure play to the insurgents' advantage. Unlike Iraq, Afghanistan has a network of undeveloped roads where it is far easier to lay traps. "Dirt roads give you plenty of softer places to dig in, then for the weather to settle it, and then for dust to camouflage it," Lt Gen Thomas Metz, director of the Pentagon's organisation in charge of seeking ways to counter improvised explosives, was quoted as saying. Even Afghanistan's most vital paved highway, the Ring Road, the primary route for commercial and military convoys between Kabul and other major cities, was built with thousands of culverts - any of which could conceal explosives, the report said. The military plans to use satellites and portable Global Positioning System devices to show convoys the exact location of each culvert, and to install monitoring systems that can detect hidden bombs, General Metz said. His unit, the Joint I.E.D. Defeat Organization, tallied 3,611 instances in which improvised explosives were used in Afghanistan in 2008, a 50 percent increase over the previous year. Besides coalition forces, even larger numbers of Afghan civilians were killed last year. The improvised bombs - buried in roads, packed into cars or bicycles and hidden in trash cans or animal carcasses - are made from materials readily available in war zones, whether abandoned bombs, construction explosives or fertilizer. They are the weapon of choice for an insurgency: cheap and easy to build, but hard to detect and counter. The Pentagon created the counter-I.E.D. organization in 2006, and its budget has ranged from $3.5 billion to $4.4 billion annually, but that does not include costs for armoured vehicles and other systems. In part because new jamming technology has foiled some weapons triggered remotely by cell phones or garage-door openers, insurgents in Afghanistan are turning to more primitive methods, using wire or even rope as the trigger. Other countermeasures being prepared include a ground-penetrating radar that only recently completed testing, as well as more jammers, wheeled robots, hardened troop transport vehicles and a laser that can detonate an I.E.D. from a safe distance. Armoured vehicles will be deployed with heavy rollers extended in front to detonate bombs triggered by pressure plates. Beyond that, the Pentagon is planning to buy 2,080 heavily armoured vehicles that are more manoeuvrable than the 2,000 larger models in place. Each costs about $1 million. The more unwieldy version of the troop transport, known as a mine-resistant, ambush-protected vehicle, or M-RAP, has trouble negotiating Afghanistan's rough terrain.