High gas prices? Other economic factors? The weather? There are as many theories as vehicles on the road this Memorial Day weekend. (If you are wondering, those numbers are below).

Whatever the question, the answer remains that travel was markedly mixed for Memorial Day 2011.

While east-west travel showed a decrease, north-south travel over I-5 showed a bit of an increase. So what about those mountain pass backups, you may wonder. While travel may have been down, it was only slightly. Combined with traffic incidents, there were places where drivers experienced significant congestion.

Both I-90 Snoqualmie Pass and US 2 Stevens Pass were busy Monday, while drivers who stuck to the I-5 corridor moving through with atypical ease.

Here are the numbers for the I-90 Snoqualmie Pass Memorial Day 2011 travel weekend (comparing 2011 with 2010):

• 181,000 vehicles traveled over Snoqualmie Pass (both directions) from Friday to Monday, a decrease of 6,000 vehicles or 3.2 percent.



• 55,000 traveled Friday, a decrease of 1.1 percent, with drivers traveling earlier, so the late-night buildup didn’t happen.



• 600 fewer vehicles traveled over the pass on Friday.



• About the same number of vehicles traveled over the pass Saturday.



• 2,300 fewer vehicles traveled over the pass Sunday.



• 50,000 traveled Monday, a decrease of 5.7 percent. Most of this decrease was in the early morning and late evening. Those noontime and early evening travelers were still met with the congestion and long waits we predicted.

I-5, Olympia to Tacoma showed a slight increase of Memorial Day weekend traffic.

• 40,600 vehicles on I-5 between Olympia and Tacoma (both directions) from Friday to Monday, an increase of 16,500 vehicles or 4 percent.



• 3,100 more (2 percent) traveled on Friday.



• 4,700 more (4 percent) traveled on Saturday.



• 3,800 more (4 percent) traveled on Sunday.



• 4,900 more (5 percent) traveled on Monday.

I-5, Bellingham to the U.S./Canadian border showed the most significant travel increase, with 133,000 vehicles on I-5 between Bellingham and the U.S./Canadian border (both directions) from Friday to Monday. This was an increase of 14,700 vehicles (or 11 percent) compared to 2010.

• 2,700 more (7 percent) traveled on Friday.



• 5,000 more (14 percent) traveled on Saturday.



• 4,200 more (13 percent) traveled on Sunday.



• 2,800 more (10 percent) traveled on Monday.

US 2, Stevens Pass Again, while those stuck in Monday’s traffic backups may not believe it, only 34,500 vehicles on US 2 Stevens Pass (both directions) from Friday to Monday. This was a decrease of 1,000 vehicles (3 percent) compared to 2010.Travel patterns for the four days appear to be as forecast.

• 600 less (6 percent) traveled Friday.



• 300 less (4 percent) traveled Saturday.



• 400 less (5 percent) traveled Sunday.



• 350 more (3 percent) traveled Monday.

While those of you who sat through the backups may not believe it, the numbers I received from our Traffic Operations show there were actually fewer drivers who crossed I-90 Snoqualmie Pass this Memorial Day weekend.

Besides Snoqualmie Pass, we highlight three other areas across the state (http://www.wsdot.wa.gov/News/2010/05/20_Memorial_Day_Travel_2010.htm) for holiday travel. Of those, traffic decreased from 2009 in two areas (I-5 through Lewis County and US 2 over Stevens Pass) and increased slightly in one (I-5 near the Canadian Border).

So, you ask, if there were 12,000 (or 5.8 percent) fewer vehicles over I-90, why was I going so slow? Friday, it was a collision that led to the eastbound backup. I wish I had a simple answer for the Monday traffic. Wow, that 27-mile westbound backup was really something.

Part of the issue is the time those 187,000 vehicles traveled. As you see in the graphs below, more people were on I-90 during "peak" hours, while not as many traveled in off-peak hours. Other theories include the type of vehicles on the road - recreational vehicles and those towing trailers or boats just don't accelerate as quick.

As you look forward to your travels this summer, we will have our forecasts available for the next two "long" weekends - Fourth of July and Labor Day, so please check them out and take notice of the peak travel times. As for other weekends? Use the tools we have available on our website and the 5-1-1 hotline. Know before you go and watch the highways signs.

Memorial Day 2010 travel weekend:

I-90 over Snoqualmie Pass

• 187,000 vehicles traveled both directions of Snoqualmie Pass between Friday and Monday, an decrease of 12,000 vehicles or 5.8 percent from 2009.
• 55,000 traveled Friday, a decrease of 3.4 percent from 2009, with most of the decrease in the afternoon.
• 2,700 fewer vehicles traveled Saturday.
• 3,200 fewer vehicles traveled Sunday.
• 53,000 traveled Monday, and decrease of 6.3 percent from 2009, with most of the decrease in volumes in the evening hours (hence the backups).

I-5, Bellingham to US Canadian border

• Friday through Monday there were 118,000 vehicles on I-5. This was an increase of 3,000 vehicles (3 percent) when compared to 2009.
• 33,700 traveled Friday, 174 less.
• 30,400 traveled Saturday, 1000 more.
• 29,300 traveled Sunday, 2,000 more.
• 25,000 traveled Monday, 200 more.

I-5, Olympia to Chehalis (Thurston/Lewis county line)

• Friday through Monday there were 254,600 vehicles on I-5. This was a decrease of 15,000 vehicles (6 percent) when compared to 2009. Maybe the rain?
• 73,700 vehicle traveled Friday, 5,400 less.
• 67,600 vehicle traveled Saturday, 4,600 less.
• 54,300 vehicle traveled Sunday, with 3,600 less.
• 63,600 vehicle traveled Monday, 1,400 less.

US 2, Stevens Pass

• Friday through Monday there were 35,500 vehicles on US 2. This was a decrease of 2,700 vehicles (7 percent) when compared to 2009.
• 9,700 vehicle traveled Friday, 290 less.
• 7,000 vehicle traveled Saturday, 1,300 less.
• 8,300 vehicle traveled Sunday, with 400 less.
  10,200 vehicle traveled Monday, with 700 less.

Click on graph to view larger: