By Matthew Wells
BBC News, Pennsylvania
At first glance, you might mistake Tom and Janis Kemp for employees at the busy Bartonsville truck stop, in eastern Pennsylvania.
Tom and Janis Kemp try to turn drivers away from "temptation"
But the place where they work is set apart from the main building, and their Western-style cowboy shirts are emblazoned with the words "Transport for Christ (TFC)".
Their chapel is a 25-metre-long (80-foot-long) office trailer that could be driven off the parking lot and onto the motorway at a moment's notice. But the Kemps are here to stay, at the invitation of the truck stop management.
"There's lots of prostitution, drugs, alcohol. We help deter that. I hope the truckers see genuine care, a place that's a haven, and can share in the hope that we have," said Janis.
The Kemps are Christian evangelicals who had planned to take the classic missionary route overseas. But instead they are using their zeal to win converts among North America's three-million-strong community of professional drivers.
With around 30 permanent "truck stop chapels" in America and Canada, TFC estimates that around 40,000 truckers visit each year, with 450 choosing to get "saved" or born again. There are also three chapels located on a busy road around Moscow in Russia.
Tom Kemp plays up his Texan roots, but despite his confidence and swagger, he acknowledges he faces powerful rivals for the drivers' attention.
About 40,000 drivers visit one of the 30 truck stop chapels each year
"One of the things you'll notice is an adult bookstore," he says as he walks around the large parking lot, trying to drum up interest in the main Sunday service due to start within the hour.
"I'm scanning the end of the trucks to look for drivers who are visible. Because these drivers work 24/7, the only time I approach them is if they're sitting behind the wheel," he says.
"We understand that on a truck stop there are lots of temptations for drivers and we provide a moral, Christian alternative while they're away from their families."
The management clearly welcomes them, supplying the Kemps with free electricity and meals.
Alice Cato, who supervises the fuel desk inside the truck stop, appreciates their calming influence.
"We had one guy who was just about losing it," she said.
"After talking to one of the chaplains he gained his composure about things and he made out good, thank God."
After a few polite refusals from truckers perched inside their huge cabs and an announcement on the CB radio and truckstop tannoy, the Kemps began their informal service with a congregation of just three drivers - all of whom were clutching their own well-worn bibles.
With no piano or pianist to hand, an old tape recorder provides the backing track to the hymns.
Among the prayers of love and support, Chaplain Tom was keen to criticise the "liberal" forces in America that he believes are threatening the religiously-inspired agenda of President George Bush.
When it comes to other faiths, however, he has a more tolerant view.
"I've had a couple of Muslim drivers come in and ask if they can put down their prayer rug and pray, I say, please... If I accept him as a man, as a person, that opens up the possibility of a theological dialogue."
One of the drivers present at the service was James Shepard, who comes from the southern Bible Belt, and works for a haulage company that is owned by an evangelical Christian.
He had just finished a run of well over 4,800km (3,000 miles) from the West Coast, and he was happy to show me around his cab, which represents home for weeks on end.
"I sometimes get on the CB [radio] and start talking about Christ. Sometimes I won't - I just pray. I try and focus more on sharing with people who'll listen," he said, acknowledging that many truckers prefer to indulge themselves in other ways.
"I even had prostitutes come to my truck to try to solicit me, and I'll try to solicit them for Christ... I've had them just break down and start crying, saying 'I know I'm wrong'."
The Kemps - who have three grown-up children - have been at Bartonsville for around 18 months now, and have not given up on the idea of maybe moving to Africa or Asia. It will be up to God to tell them, they say.
Meanwhile, they spend much of the week apart, with Jan holding down a TFC job in their home town, more than 320km away.
Always willing to look on the bright side of what can be a fairly seamy and compromised world, it allows them to empathise better with the truckers who they serve, said Janis.