(CNN)In one horrifying moment, on a lonely road in Bolivia, Tim Bridgman lost his soul mate.
He and his wife Sharon had been riding their bicycles around the world to raise money for ShelterBox, an all-in-one disaster relief kit with a tent and lifesaving supplies. They had set out in June 2012 from Nordkapp, Norway, and were more than halfway through their journey when Sharon was killed.
The couple, who did not have children, planned to journey from Scandinavia to South Africa, then from Argentina to Alaska on mountain bikes. They had belonged to a cycling club for more than a decade. (Tim, a carpenter, lived with Sharon in Devon, England. She was a drug and alcohol addiction counselor.)
"I've always wanted to cycle around the world, but not the easy way," Tim, 42, says. "I wanted to cycle the two longest land masses in the world. She looked at me and said, 'Let's do it.' "
Photographs on Tim's website, north2northcycletour, show glowing progress reports from the loving couple. Sharon seems to travel back in time as she uses a well on a Romanian hillside, with a long wooden lever and a bucket. The couple leaps above their bikes in jubilation when they reach a monument at the meeting point of the Atlantic and Indian oceans in South Africa. They trek though South America as a tailwind of goodwill from strangers, family and friends helps push them though unfathomable muscle fatigue, scorching temperatures, freezing conditions and whipping winds.
But in Bolivia's Antiplano, this romantic tale got crushed by heartbreaking calamity on April 26, 2014.
"It's like being up on the moon," Tim describes the Altiplano. "We're up at 4,000 meters, more than 15,000 feet, and there is no one... Sharon was hit by the only car, a Toyota Land Cruiser, within nine hours."
So their journey took the ultimate U-turn, back to the church in Devon, where Tim and Sharon married in May 2008. Sharon was buried there.
Tim grieved for several months, then decided to complete the quest he and Sharon had begun. He mounted his bike and pushed himself forward.
"I realized I had to come back and not only finish (the bicycle trip) for her, but to finish it for me to learn to live again," Tim says.
Tim grabbed a box full of letters friends and family wrote to Sharon -- "Things people wanted to say to her but never got the chance" -- to take with him.
Knees aching, heartbroken, dreams of growing old together gone, Tim returned in March 2015 to the desolate Altiplano road where Sharon was killed and saw a modest memorial with a small cross strangers had built.
"I wanted to say something meaningful, but my voice wouldn't work and only a few choked words came out," Tim wrote in his blog that day. "What could I say? I had lost the most precious thing I had ever had. "
The carpenter dug a hole to bury the box of letters to Sharon, along with an empty bottle of Argentinian beer they had enjoyed drinking together. Then he climbed back on his 14-speed, Surly Troll bike.
Several days after, Tim traveled a pathetic 10 miles in 9 hours, wheels sinking so deep in salt flats he found and rode on railroad tracks because they offered an intermittent hard surface. When Tim finally reached a small mining town, he was greeted by a smile-inducing fur ball, a fuzzy, four-legged welcoming committee.
"This amazing dog," Tim grins. "He almost congratulated me into making it. So it was a nice end to hard day."
It's the the treasured moments with animals, and the kindness of strangers that motivate Tim.
"People praise me, but it's not that hard," Tim says. "I meet people who are picking up aluminum cans just to make a few pence for their family. I have a passport, freedom... I have met thousands of people who would never get the chance to have a passport, let alone travel around the world."
Tim has traveled through 40 countries, and logged more 34,000 miles. He estimates he has altogether climbed 100 miles higher than the International Space Station, on two wheels. He has raised almost $40,000 for ShelterBox so far, $25,000 from Rotary Clubs, which also have provided food and places to sleep.
He doesn't travel with a ShelterBox tent, which is 14 x 14 feet and 7-feet tall. It's too bulky and heavy to haul on a mountain bike, but perfect for a family that's homeless and stripped down to rags after a typhoon, flood, fire or other disaster. The box also has thermal blankets, cooking supplies water purification units, building materials, corrugated iron, metal strapping and nails.
Tim's bittersweet, four-year voyage will end in Prudhoe Bay, Alaska, in about six weeks. He vows he will arrive filled with the wonderful moments he shared with Sharon and memories no one can take away.
"And when I get there (Prudhoe Bay) I'm going to go to bed. and I am going to sleep for about a year," he says with a laugh. "And I am going to get up and have a pint (of beer) and an English pie. And then after, I'll have to figure out how to rebuild my life."