That confused me too. The tone suggests they think it's suicide, but more than twice as many people that age die in traffic accidents. Maybe I'm misinterpreting. Certainly not "all too clear" though. US 20-24 years fatal crash rate: 36.3/100,000 [1], and US 15-24 years suicide rate: ~15/100,000 [2].
The UK has about 1/4 the rate of traffic deaths [1], and possibly even more than that in young people. Although it also has 1/2 the rate of suicides (no idea about age distribution though).
Any idea what this "clear" cause is?