After a week of tolling, state transportation officials said average travel times on I-405 are on par with the same period from last year. There were more than twice as many collisions on the interstate, however.

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Although traffic volume on Interstate 405 continued to rise over the past year, travel times remained near or below 2014’s weekday average for last week, the first week of tolling, state transportation officials said in a news conference Monday.

However, collisions on the interstate rose sharply from the same time period last year, and state troopers were busy last week warning drivers and making sure they understood how to use the roadways. Eleven drivers were caught avoiding tolls.

Washington Department of Transportation Assistant Secretary Craig Stone, who oversees tolling, said he expects the numbers to change as drivers adjust.

“We’re still in a settling period,” Stone said at the event, intended to give baseline information about how the tolls worked. “Travel times were generally in the range we’ve seen in the previous year.”

That’s despite a 5-10 percent increase in traffic volume on roads since last year that Stone credited to economic growth in the region.

Stone said the data could indicate that I-405 is more efficient on weekdays with the new express toll lanes.

“We’ve seen benefits in the general-purpose lanes,” Stone said.

Drivers paid an average of $1.50 to travel south in express toll lanes, and $1 to travel north. He said drivers saved 15-17 minutes by choosing to pay the toll. More drivers ventured into the toll lanes later in the week, he said.

The toll, which can vary from 75 cents to $10, reached a high of $5.25 last week, after a southbound crash in the Canyon Park area at 6:30 a.m. Friday.

Regional traffic operations administrator Mark Leth said traffic in express toll lanes moved briskly throughout the week. He said cars were able to travel at 45 mph or faster at least 90 percent of the time, considered the “sweet spot” for maintaining high capacity on roads.

Stone said the agency does not believe drivers are choosing other major arterials such as Interstate 5, instead of the newly-tolled highway.

“We’re not seeing diversion from 405,” Stone said, adding that the state would have more detailed information about tolling’s effect on local routes later this month.

Washington State Patrol Trooper Chris Webb said there were 119 collisions on I-405 last week, compared to 48 last year. He said he could not yet pinpoint a reason for the increase in collisions.

He said his agency handed out 40 tickets and 358 warnings on I-405 last week. The figures include stretches of road outside the 17-mile tolled area.

“We’ve concentrated on trying to educate people with warnings,” Webb said.

Webb said the most common infraction was drivers crossing the double white lines that separate the toll and general-purpose lanes, which will lead to a $136 ticket when troopers’ generosity runs out.

He said he worries drivers will try to illegally merge into the toll lane when traffic’s stuck, with cars coming in the toll lane at high speeds.