Heat kink at West Hyattsville (Photo credit: WMATA)

If it feels like Metro is being extra sluggish this afternoon, it’s because it really is—orders were giving today for trains to travel no faster than 35 mph on above-ground segments if the tracks get too hot. And too hot they got as of 2:30 p.m., when the order was given to abide by the speed restrictions. In a press release, Metro explained how and when the call is made:

The decision to implement “slow orders” for portions of the rail system will be based on several criteria, including the actual temperature of the rail. Metro track inspectors routinely measure rail temperature using a number of devices including infrared thermal “guns” and direct contact gauges. The combination of direct sunlight and high ambient temperature can cause rail temperatures to reach 135 degrees or higher. On particularly hot days, Metro implements a regimen of enhanced track inspections, with additional inspectors and supervisors walking and riding the system for signs of heat-related issues.

Under the new practice, if inspectors detect rail temperature higher than 135 degrees on a section of rail, a slow order will be placed into effect for that rail line. However, Metro officials may implement slow orders using other, more conservative criteria, including an average median temperature, during periods when the region is experiencing a prolonged (3-day) period of heat with insufficient nighttime cooling.

Ten days ago, a Green Line train derailed after excessive temperatures caused a “heat kink,” or a distortion of the tracks. High temperatures are expected through tomorrow.