It's something to think about while you walk or drive home from work: will Boris Johnson's plan to rephase traffic lights, giving up to six seconds more time for traffic and less time for pedestrians, actually work?

Will a new digital countdown at the end of the "green man" phase encourage walkers to hot-foot it to the other side? Or will crossing the road become a death-defying feat?

The Evening Standard decided to find out with a snapshot survey of some of the busiest junctions in central London.

Pedestrian crossings are set to the green man for a minimum of four seconds. Time is added depending on the road width and average level of use.

We found wide variations in the length of the green phase for pedestrians. But in almost all cases, there seemed to be ample time for able-bodied people to cross.

In parts of Parliament Square, known for rapid phasing to keep traffic moving, there is only a second to spare, with green for walkers lasting five seconds. In Trafalgar Square a complicated system of lights on one-way sections usually allows plenty of time to cross at six seconds.

The green phase at the junction of St Martin's Lane and Long Acre allows almost 20 seconds. In Euston Road, at the junction with Gordon Street, those going to and from Euston station have 30 seconds, while traffic going north and south clears easily and drivers heading east and west sit fuming.

The Standard asked Londoners how they felt about the plan. Student Holly Remdel, struggling with a suitcase at Piccadilly, said: "It is a terrible idea. It is a very short time when you are pulling something heavy behind you."

Retired insurance executive David Salmon, 76, from Henley, said: "I would be against it. Pedestrians need priority in built-up areas."

But Kevin Copley, a black-cab driver, backed a change: "There's no consistency or rationale to these crossings. What is the point of having to wait when no one's crossing?