According to UK experts, the transition between primary and secondary school, when children often begin to walk to school unassisted, can be a particularly risky time.
In some countries, such as the UK, road safety education and legislation encouraging drivers to slow down appears to be having the desired effect, reducing road accident rates, says the WHO report author, Dr Anthony Costello.
But other countries are lagging, he says.
The other big killers
Globally, adolescent deaths as a whole have been reducing.
But some fatalities are becoming more commonplace.
Deaths from self-harm are increasing in many regions, says Dr Costello.
“Self harm is a massive and increasing issue in many countries. We are seeing suicide rates go up.
“Adolescence is quite a stressful time of life. Young people need support, but adolescent health across the world has been largely neglected.”
He says improving the way health systems serve adolescents is just one part of improving their health.
“Parents, families and communities are extremely important, as they have the greatest potential to positively influence adolescent behaviour and health.”
The Global Accelerated Action for the Health of Adolescents report was produced by the WHO in collaboration with UNaids, Unesco, UNFPA, Unicef, UN Women, World Bank, the Every Woman, Every Child initiative and The Partnership for Maternal, Newborn, Child & Adolescent Health.