The state transportation department said Tuesday it was rolling back recent speed limit increases on some highways, including a stretch where a Madras woman and her three children were killed in crash last month.

The state raised speed limits in March on eight eastern Oregon highways from 55 to 65 mph, and to 60 mph for trucks. They include stretches: U.S. 20, U.S. 26, U.S. 97, U.S. 197, U.S. 395, Oregon 31, Oregon 78 and Oregon 205.

But those increases will be rolled back on four stretches:

16.5 miles of U.S. 97 from Madras to Terrebonne

A mile of U.S. 97 at the La Pine south city limit

6 miles of U.S. 20 from the Bend east city limit to Dodds Road

11.5 miles of U.S. 20 from Vale to Cairo Junction.

The transportation department said it was reducing the speed limit by temporary order after new engineering analyses and reviewing crash data. It will decide, with the state Speed Zone Review Panel, whether to make the newest change permanent over the next year.

New speed limit signs will take effect when they're posted, expected in the next two to three weeks.

The stretch from Madras to Terrabonne includes an intersection where a van driven by Anita J. Bemrose, 49, was rear-ended by another driver on May 18 while stopped to make a turn. The impact sent the van into the oncoming lane, where it was struck by another vehicle.

Troopers said the cars were traveling within the posted speed limit, but it's not clear if the increased speed limit was a factor. The Oregon State Police declined to release the report to The Oregonian/OregonLive last month, saying the investigation was incomplete.

The Oregon Legislature ordered the speed limit to be raised in a bill passed last year. It also raised speed limits on much of Interstates 84 and Interstate 82 to 70 mph from 65 mph.

Research for the National Cooperative Highway Research Program in 2006 found increasing the speed limit from 55 to 65 mph raises the number of crashes by about 3 percent, while the number of fatal injuries increases by 28 percent. However, individual states have reported mixed results upon raising speed limits.

Transportation officials said last month it cost about $1.5 million to implement the higher speed limits, including installing new signs and re-striping roads.

-- Elliot Njus

enjus@oregonian.com

503-294-5034

@enjus