The provincial government announced plans in December to improve safety along Highway 16, including funds for traffic cameras and vehicles for indigenous communities. But little has changed on the road, which lacks lighting or any public transportation other than infrequent Greyhound bus service that does not reach remote communities.

The perils do not stop desperate people from thumbing rides in a region where public transportation is practically nonexistent. Just outside the village of Burns Lake, Drucella Joseph, 25, an unemployed aboriginal woman, eagerly climbed into the back of a passing car along with her boyfriend, Corey Coombes. “Friends will drive me when I really need a ride, but other than that, we just hitchhike,” she told the driver. The couple gets by on his disability payments and on donated food from food banks. Neither has a cellphone. When hitchhiking, Mr. Coombes says he protects himself by carrying a club or a screwdriver.

British Columbia is infamous for serial killers and criminals who often targeted aboriginal women. In 2007, Robert William Pickton, a pig farmer, was convicted of killing six women, though the DNA or remains of 33 women were discovered on his land. Many of them were aboriginal. One of Canada’s youngest serial killers, Cody Legebokoff, was 24 when he was convicted in 2014 of killing four women near the Highway of Tears. David Ramsay, a former Prince George provincial court judge and convicted pedophile, was imprisoned in 2004 for sexually and physically assaulting indigenous girls as young as 12.

Anguished family members said they received little help from the authorities, a sharp contrast to the cases of missing white women. After Ms. Chipman vanished in 2005, her aunt, Ms. Radek, said the police objected to the family putting up its own missing posters. “They knew we were searching day and night, and they did nothing to help us,” she said. The next day, she said, a white woman disappeared near Vancouver “and the police were out in the streets putting up posters.”

After her daughter Ramona disappeared in 1994, the police refused to act, said Matilda Wilson, a member of the Gitxsan First Nation. “They gave us all these different excuses that she might be back tomorrow or next week,” Ms. Wilson said. “There was no hurry or alarm about it, so we started looking ourselves.”