How gratifying to return from a week away to be greeted by side roads with smiling 20 mph roundels and the message on a bright yellow background, “It’s twenty for a reason”.

Cycling around, my experience so far is that most drivers are obeying the limits. On some roads, it makes a huge difference that cars are going slower. Perhaps one reason most drivers are playing ball is that they or their families are cyclists.

Like other drivers, I missed the larger “entry” signs as I drove up Morrell Avenue – maybe they haven’t been put up yet – but saw the small repeater signs and regulated my speed. I don’t think other drivers realised why.

Obviously, a blanket limit of 20 mph for the whole city would make it easy to know your limit – especially as the 30mph arterials are precisely where cycle and pedestrian traffic is highest.

The Oxford Mail speed test on cars heading down Morrell Avenue was bound to find speeders. People have always been tempted to go too fast down that hill.

Cyclists will be glad it’s included in the 20mph zone though. It’s a lot more treacherous than it looks. Drivers doing 25-35 weave in and out between the parked cars and are encouraged to accelerate by the road’s occasionally generous widths, often cutting cyclists up, driving much too close and fast.

Despite my best efforts to help them see the light, I know a lot of people in Oxford refuse to cycle because “it’s too dangerous”.

While I know that a dose of cycle training would equip them with the skills and the confidence that they need to deal with any situation, I do sympathise. The two factors that make anywhere “too dangerous” are (a) the speed at which vehicles pass; and (b) how close they pass, especially buses.

Anyone would feel intimidated by the rush of air and the whoosh of engine as a vehicle rushes past too quickly and too close. It’s not that buses pass closer or faster than cars, but it feels a lot scarier if they do.

Much as I’d like to think it’s to encourage cycling, the bottom line is the council has reduced the limits to 20mph to reduce accidents. Hit by a car at 40 mph, a pedestrian has an 85 per cent chance of being killed while at 20 mph the risk falls to just five per cent.

Children’s deaths and injuries should be reduced by 67 per cent now 20mph is the speed limit on residential roads.

The real victor in the 20 mph debate is everybody who lives in the city. The civilising effect of lower speeds makes streets much pleasanter places. At 20mph, drivers have eye contact with the people in the street: cyclists and pedestrians know they’ve been seen and drivers are less inclined to muscle their way along “their” road, more inclined to share the space. At speeds over 30mph, drivers see less and care less. Speeding cars destroy communities.

Lower city speeds benefit drivers, too. If the arterials were 20 mph as well, there’d be less need for traffic signals and the queues they cause.

Slow-moving cars require fewer controls and allow a more efficient city, with no accelerating from one queue to the next. Motor vehicles and cycles merge with ease at 20 mph, and pedestrians can cross roads, too.

“It’s twenty for a reason” – hallelujah!