Standing on the Maiden Moor ridge above Derwentwater last Sunday, I was at once depressed and exhilarated. Depressed because I had overestimated my strength and stamina – a common fault among men of a certain age. I'd thought I could whip round the six magnificent peaks that surround Newlands Valley and be at the jetty at the foot of Catbells to catch the last boat to Keswick at 4.40pm.

But its departure time came and went and I was still three miles away and 500m above the shoreline. From my viewpoint I could just glimpse a speck in the distance floating across the lake without me. My despair did not last. The sun was shining. (In the Lake District! In March!) The clocks had moved forward that morning and I had light until 8pm. I could keep walking without anyone or anything stopping me. I trudged down the long ridge and followed the path to Keswick through woods and fields. The change in colour and mood as mountain turned to valley, and the glimpses of the first buds on trees, were indeed exhilarating, until I reached Keswick and re-entered the Britain where the interests of walkers come last.

The path stopped just before a T-junction where the main route out of town meets a side road. One branch of the T leads to Keswick's bus station. People famously run for buses, but there was no pedestrian crossing to take them across the road. Even in a national park that sells itself as a place where walkers can escape our odious streets, the authorities had not taken basic precautions.

"One day a driver will kill someone here," I thought.

The next evening I picked up the Carlisle News and Star and found that while walkers around Keswick had been spared, four people had died on Cumbria's roads that day. The crashes made the local press, but the nationals did not bother with them. Death comes so often on the roads, its visits are not worth covering: particularly when the dead were on foot.

As I was climbing fells and missing boats, the London assembly was issuing a doubtless vain appeal to stop the killing of walkers. More pedestrians are killed or seriously injured on London's streets than any other type of road user, its members said.

They were "astonished" to find that a quarter of the deaths occurred on pedestrian crossings – which are meant to be places of safety. Others were inflicted by bus drivers, who, despite being privatised, are meant to be publicly accountable, and by the drivers of heavy goods vehicles, who are also meant to meet minimum safety standards.

Few in authority cared. Not one of the Metropolitan police's 32 boroughs listed the enforcement of traffic law as a priority. Deaths on the road are to today's criminal justice system what domestic violence was in the past: as natural and inevitable as the weather.

What applies in London applies nationally. You would never guess it from British society's obsession with crime but there are three times as many road deaths each year as there are homicides. As the campaign group Road Peace says, the budgets for collision investigations are tiny when set against the resources the police throw at murders.

If I write with feeling, it is because I have become a regular walker for the first time since I was a teenager. Eighteen months ago, I discovered that 17st 8lb could not be defined as a "cuddly weight", as I had imagined, but according to something called body mass index was better described as "clinically obese".

I got down to 13 stone by heeding the NHS's wise advice to ignore fads. Rather than following the Dukan, Atkins, Paleo or 5:2 diets, I created my own "do what your mother told you diet". If you wish to join me on it, you should:

■ "Eat your greens" – although not even my mother foresaw a 21st century where nutritionists at University College London would insist on people eating seven portions of fruit and vegetables a day.

■ "Stop scoffing all the cakes."

■ "Stop eating between meals."

■ "Never dare come back to my house in that state again" – it turned out that four pints of bitter and a large bag of crisps before dinner are fattening.

■ "Get some fresh air."

In my case, trying to get some fresh air means walking whenever I can. It was only when I trudged their streets that I realised how the designers of Britain's towns and cities barely thought of walkers. Pelican crossings take you to traffic islands in the middle of main roads and leave you there. And it's not just bus stations: hospitals, including the vegephile nutritionists' own University College hospital, fail to provide safe, direct access for patients who might be trying to reach their entrances from the other side of the road.

As the overweight British turn into a nation of human space hoppers, as global temperatures rise, and pollution burns our eyes, you might have thought politicians would encourage us to walk.

Yet Britain does not have a "walkers' lobby" to apply pressure. Walking is the victim of a paradox identified by Mancur Olson Jr and Susan Lohmann in the 1960s. Special interests triumph over general interests in democracies, they said, because special-interest groups are highly motivated: cyclists, for instance, are finally getting a hearing because they tend to be young, professional and articulate. (I'm not knocking them. Despite myths to the contrary, cyclists hardly ever injure pedestrians.) Special interests can raise money for lobbyists and persecute politicians if they don't, in the case of roads, listen to the AA, RAC and Road Haulage Association. No powerful lobby, however, upholds the general interest in being able to walk without constraint or danger. There's no money in it and everyone expects someone else to put in the hard work.

What Margaret Thatcher called the "great car economy" is dying all over the world. Even if you can ignore the wrecked environment, people no longer want to live, work or establish businesses in landscapes that are overwhelmed by cars. The most forward-thinking cities are following the Vision Zero model, developed by Swedes in the 1990s. They produced the road traffic equivalent of zero tolerance of crime. No death on the roads is acceptable, governments from the Netherlands to Bill de Blasio's New York now join Sweden in saying.

In aviation and every other perilous occupation, regulators take human error for granted. On the roads as in the air or in nuclear power stations, you cannot just blame people for making mistakes, but should design accidents out of the system by cutting speeds, drastically when necessary, and building barriers to prevent collisions.

Not in Britain. The coalition abandoned targets to reduce road deaths so it could honour the Tories' promise "to end the war on the motorist". They did not stop to consider the mewling vacuity of their self-pitying slogan. Conservatives complain about others playing the victim card but, without a blush of shame, talk about "the motorist" as if he were a victim of Bashar al-Assad and imagine a "war" in which the enemy is a child who runs into a street. They follow that dismal reasoning by transferring the generalisations of identity politics to road safety. It never occurs to them that there is no such thing as "the motorist": the man or woman who only drives. Everyone walks. And, unless they're on the fells, everyone crosses roads.

In 1947, JS Dean, then president of the Pedestrians' Association, produced a robust polemic in which he explained at length how the prewar countries that tolerated the highest level of road deaths were fascist Italy and Nazi Germany, with their contempt for life and cults of murder. "Scratch a road hog, and you'll find a fascist," he declared, before asking a good question. When else in history has humanity lived with the "foul, strange and unnatural" belief that it should be "common custom to kill and maim people because they get in your way"?

Almost 70 years on, that foul and unnatural belief remains as prevalent in Britain as ever.