SEATTLE - Traffic engineers have officially extended Interstate 5 southbound express lane service by one hour on Saturdays and Sundays. Beginning tomorrow, the I-5 express lanes will regularly close southbound at 1 p.m. and reopen northbound by 2 p.m. on weekends.

While both directions of traffic on I-5 are heavy with approximately 123,000 vehicles traveling northbound and 112,000 vehicles traveling southbound on an average Saturday through Seattle, WSDOT engineers found that southbound traffic has been experiencing a larger percentage of delays in a recent traffic study.

"During peak weekend travel times, we found that southbound I-5 drivers are experiencing longer back-ups and more delays when compared to northbound congestion then dirvers on northbound I-5," said traffic engineer Christina Strand. "This change will more evenly distribute delays experienced by drivers traveling into Seattle on I-5 in both directions."

Extending southbound express lane service until 1 p.m. is nothing new to drivers on Saturdays when the Mariners are in town. On weekend Mariner game days the express lanes usually do not reverse until 1 p.m. to allow game traffic time to get into Seattle. Traffic engineers compared data collected from these weekends with data collected from typical weekends and found out that while northbound drivers experience a spike in congestion when the express lane reversal is delayed until 1 p.m. persistent southbound back-ups are reduced by one hour.

Over the years traffic engineers have continually monitored traffic on I-5 to determine the best schedule for the express lanes. "We will continue to evaluate the current operating schedule of the express lanes to ensure the system is benefiting all drivers." Strand said.