It's a question your life could depend on: do you know what a truck driver can't see from behind the wheel?
The answer may come as a bit of a shock to many of the millions of motorists, cyclists and pedestrians who have to share roads with HGVs.
For lorry drivers have blind spots all around their vehicle, even to the front...
Even when cabs are fitted with extended view mirrors, as is compulsory under London's Safer Lorry Scheme, drivers cannot see everything. There are still significant blind spots to the front, rear, off-side and near-side.
"It amazes me that we allow these big, heavy vehicles onto our streets when the drivers' vision is so restricted," said Chris Hanson-Abbott OBE, of road safety campaign SteerSafe.
"It is a matter of life or death. People die in driver blind spots while the technology that eliminates these blind spots sits on the shelf ignored by government and the HSE. Most glaring is The London Safer Lorry Scheme having ignored this technology too, making a fiasco of the Scheme.
If drivers, pedestrians and especially cyclists could see just how little a driver can see the roadway close to his vehicle most of them would be too scared to take to the road.
Not only can a truck driver not see directly behind his truck which creates a reversing hazard it is also difficult to see a vehicle tailgating him.
"If more car drivers, pedestrians and cyclists knew how big are the gaps are in a truck driver's field of view they'd be horrified."
Most people are aware that a lorry driver cannot see directly behind the vehicle, which creates dangers when a lorry is reversing but also makes it impossible for a lorry driver to be aware of a vehicle that is travelling close behind.
However, fewer are aware of the blind spot to the right, and also of the most dangerous blind spot of all – the one directly in front of the lorry. Accidents in this zone are more likely to be fatal.
Researchers at Loughborough University analysed a year's worth of HGV accidents in which police recorded that blind spots were a factor. They found that, while only five per cent of those accidents occurred in the front blind spot, they accounted for a staggering 30 per cent of the fatalities.
Accidents in the rear blind spot were the second most deadly, accounting for 25 per cent of fatalities, followed by those in the near-side blind spot (17 per cent) and in the offside one (six per cent).
The front blind spot is due to the height of the driver's cab and also to the left and right windscreen pillars.
The Class V and Class VI extended mirrors that are required under the London Safer Lorry Scheme do assist vision into the near side and front blind spots respectively, but they don't cover all the gaps to front, left and right.
Hanson-Abbott, who was awarded the OBE for services to vehicle road safety, said: "All these blind spots would be eliminated by fitting cameras that give a bird's eye view of all of the activity around their vehicle. The technology is readily available – what price a life?