Port Authority spokesman Jim Ritchie said about 20 bus routes remained out of service today, and numerous other routes were detoured or shortened because of poor road conditions. Delays on most routes ranged from 30 to 45 minutes but a few delays exceeded one hour. The HP Holiday Park route had delays of one hour, 15 minutes.

Service on the Light Rail Transit system operated without serious problems, except for the 52 Allentown line, which remains out of service. Crews worked through the night to keep ice and snow from accumulating on the overhead wires that supply power to rail vehicles, Mr. Ritchie said.

He said the authority is hoping that conditions will improve for the evening rush. Buses will continue to face possible weather-related detours and delays. Updates will be posted on the authority's website, portauthority.org and on Twitter (@Pghtransit).

The bus routes that are not operating:

6A Troy Hill Road, 6D Spring Looper, 11E Fineview, 41E Mount Washington, 43E Mount Washington Express, 44D Jefferson, 44E Inglewood, 44F Terrace, 46K Knoxville, 52 Allentown, 56U Oakland-Greenfield, 74A Homewood-Squirrel Hill, 81A Oak Hill, 81C Webster, 84A Herron Hill-Oakland, 84B Oakland Loop, 84C Hill Loop, 89A Garfield Heights and 94C Paulson Avenue.

Many of the routes that are operating have detours because of poor road conditions. Riders were advised to use bus stops along main roads. Delays and changes to routes are likely.

The Mon Incline is open. The Wabash Tunnel HOV lane is closed.

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