When a vehicle approaches a checkpoint at speed, ignoring warning signs to slow down, troops do not know whether the driver is simply careless or a suicide bomber.
This makes it necessary for troops to have a clear and harmless way of forcing drivers to stop.
Green laser dazzlers designed to temporarily blind drivers were sent to US forces in Iraq and Afghanistan for just this purpose.
But at short range they can damage the eye, and a number of US troops and civilians have ended up in hospital with eye injuries after "friendly fire" incidents.
US troops and civilians have been sent to hospital with eye injuries after 'friendly fire' incidents.
Now, according to a report in New Scientist, the US Department of Defense's Joint Non-Lethal Weapons Directorate (JNLWD) in Quantico, Virginia is developing a pulsed laser designed to prevent eye damage.
Its wavelength means a portion of the light is absorbed by the vehicle windscreen, vaporising the outer layer of the glass and producing a plasma.
This absorbs the rest of the pulse and re-emits the energy as a brilliant white light that is dazzling but harmless.
Because the light is emitted from the windscreen, the effect on the driver's eyes should be the same regardless of the vehicle's distance from the laser.
According to Scott Griffiths of the JNLWD, a working prototype could be ready by next year.