Hot potato for Japan's traffic authorities

The baked sweet potatoes, or yaki-imo, he sells have long been enjoyed by Japanese kids and adults alike, and the way these tasty snacks are prepared is as natural to the locals as slurping a bowl of noodles.

But anyone who has closely examined one of the mini-trucks that sell yaki-imo throughout Japan might not agree. They are basically giant barbecue ovens perched atop petrol tanks on the back of 660cc mini-trucks.

In what could easily be described as a time-bomb on wheels, they combine dry kindling, excessive heat, visible naked flames and a cast-iron oven with 40 litres of highly flammable fuel in the petrol tank.

“I can see why you might think that,” says our neighborhood yaki-imo vendor, 61-year-old Kenji Shimizu. “But all yaki-imo vendors are very aware of the potential danger and operate in ways to ensure safety.”

I watch Shimizu add extra wood to the fire, and within just 30 seconds his oven has become a raging inferno, generating heat that can be felt metres away.

But while this jovial yet quietly spoken man has been selling sweet potatoes in this way for more than a decade, steering his way through neighbourhood streets as he plays catchy jingles over his loudspeaker, that fire still seems awfully close to the petrol tank.

“We fit heat-absorbing insulation between the oven and the fuel tank, we drive very slowly and we only fire up the oven after we’ve stopped the truck,” Shimizu tries to reassure me.

Self-regulation is all well and good, but we doubt there's anywhere else in the developed world that a government would allow such a vehicle on the road.

Besides, although we don't doubt Shimizu’s own personal responsibility, I’ve seen yaki-imo trucks zip past police patrols in Tokyo at more than 50km/h with fires burning brightly in the back. I’ve never seen one pulled over, though.

I’m also amazed that the manufacturers of these trucks – most commonly the Suzuki Carry and the Daihatsu Hijet truck – have not entered the fray and tried to improve safety. But then it’s not their problem.

To get the other side of the story, I dropped into my local police station to find some answers. The veteran sergeant in charge was as bewildered at my queries as I am with the dubious modifications made to these small trucks. He was not sure which department had jurisdiction over the mini-trucks, but confirmed that the police did not.

“In my 32 years on the force, I’ve never heard of any accidents involving yaki-imo vendors,” says the perplexed plod. “They are just part of the landscape. They were around for decades before I was born and I grew up seeing them everywhere. We don’t think twice about them.”

But if the police are not licensing or inspecting these trucks, then who is? Certainly not the hygiene section of the insurance and welfare department at the local ward office, which licenses food preparation vendors. They said they had nothing to do with sweet potatoes, and suggested we try the Fire Department, “because these trucks handle fire.” Makes sense.

Not surprisingly though, the Fire Department replied that their jurisdiction covers buildings only — not moving vehicles.

The Ministry of Land, Infrastructure and Transport said they had no firm guidelines for such trucks either, but they did suggest we try the government-run Mini-vehicle Licensing Inspection Association, where a bureaucrat who did not want to be named coughed up some facts about this hot potato issue. Talk about the run-around.

He explained that yaki-imo vendors first appeared on the streets of Japan more than 100 years ago, using hand-pulled two-wheeled trolleys. Then, as the age of automobiles arrived, the large cast-iron ovens understandably found their way onto the back of trucks. And no one, including the Japanese authorities, seemed to pay any attention.

In fact, the Mini-vehicle Licensing Inspection Association defines these vehicles as “mini-trucks carrying removable loads.” This means that when they are inspected at the police pits to secure their registration, all the vendors have to do is remove the oven from the back, pass the inspection and then refit the oven again -- a practice many vendors appear to follow.

“These street vendors, who have been around from before my grandfather was born, have fallen through the cracks in the system as new road laws on seat belts, drink-driving and in-car mobile phone use have been passed,” one policeman coughed up. Aha! The truth at last.

But it seems that as long as their trucks don’t cause any fires or blow up, Japan's yaki-imo men will be left to operate as they have for a century or more. It’s a sweet deal, so long as nobody gets scorched.