Compared with recent years, the Maryland Transit Administration hasn't been doing too badly with its MARC service this summer -- until Friday.

With temperatures soaring to well over 100 degrees, the MARC system was plagues by multiple equipment failures that delayed trains up to 75 minutes. The MTA reported that the electric wire that power the trains on the Penn Line were sagging in the heat, forcing single-track operations between Washington and New Carrollton. An Amtrak train that became disabled at New Carrollton had been removed by 6 p.m.

In addition to the usual hot-weather restrictions on the Camden and Brunswick lines, a heat order was issued for the Penn Line holding speeds to 80 mph.

Penn Line Train 443, the 4:50pm departure from Penn Station to Washington, was cancelled, leaving passengers to wait for the 5:20 and 5:25pm trains. The 3:23 p.m. and 4:10 trains out of Washington were running more than 50 minutes late. The 4:20 p.m. out of Washington left Union Station about a half-hour late and was approaching New Carrollton at a crawl, a rider reported. By the time it reached Halethorpe it was running 75 minutes behind schedule. It finally arrived in Baltimore shortly after 6:30 p.m. -- completing a trip of more than two hours.

The 3:30 p.m. Camden Line train out of Baltimore was running a half-hour late as it approached Dorsey on heat-restricted lines that could cause further delays.

With temperatures this high, cascading troubles can be expected through the evening.