WASHINGTON >> An unprecedented daylong shutdown of the Washington area’s Metro subway system will force commuters to spend a day without their most reliable form of transportation — and the source of their constant complaints.

Ridership on Metro has dipped as the system’s reliability has deteriorated, and gripes on social media occur daily.

Still, more than 700,000 people hop on the trains every day because it’s still the best way to get downtown from Maryland, Virginia and the city’s outer neighborhoods. On Wednesday, they won’t have that option.

The nation’s second-busiest transit system was shut down at midnight Tuesday for a system-wide safety inspection of its third-rail power cables, prompted by a series of electrical fires. It will reopen at 5 a.m. Thursday unless inspectors find an immediate threat to passenger safety.