Around 50% of the global oil supply passes through a maritime chokepoint, according to the US Energy Information Agency.
Chokepoints, defined as narrow channels along widely-used global sea routes, range from stable and secure to political and dangerous. In many cases, however, there's no viable way around them.
For a closer look at them, we've visualized tanker traffic density over the past 14 days at each location, using a tool provided by vessel-tracking company FleetMon.