. >> reporter: derrick wartd, news 4. >>> stay with news 4 for continuing coverage of the record-breaking heat and visit nbcwashington.com for chuck's latest forecast as well as a list of cooling centers. >>> the heat caused a metro train to derail yesterday near the west high hyattsville station. the long, dark journey for passenger whose had to take the tunnel to get out. the latest on what went wrong and what metro is doing to keep riders safe in this excessive heat. darcy? >> reporter: yesterday's derailment is affecting service through metro systems across the area. that's because metro has ordered all of the trains that operate above ground to keep it under 35 miles per hour. that may add some time to your trip. then some stations like here at west hyattsville station, they're offering shuttle buses while the track repairwork continue continues. >> a couple more -- >> reporter: this video taking by a gazette reporter walking through the darkened tunnel yesterday afternoon on the green line train when it derailed. >> shifted from side to side. and going extremely fast. >> reporter: d