The last time I sat in stop-and-go traffic on SR2, I had ample time to sit and think about how cool it would be if I could know when it would be wise to delay my trip a few hours in exchange for a smooth commute over the mountains. I have two young kids, and there's nothing less fun than a 9 month old baby screaming in the back seat as you slog through Gold Bar at 3 MPH.
Anyways, as I thought about the problem, I started wondering if the WSDOT had traffic volume data for this area. I went home and after some Googling, found WSDOT's annual Peak Hour Traffic Report, which is a list of the highest volume hours of the year at WSDOT's Automated Data Collection sites. While there is no data collection site in Sultan, the closest one is in Skykomish, which is about 30 minutes to the East of Sultan.
I emailed WSDOT and they provided me with some raw data for the Skykomish location, and I created the following graphs that represent peak hour traffic during the year of 2007. (Special thanks to Jim from WSDOT for his help on this).
Some notes:
- The data is listed by hour and by date, with major holidays labeled so we can get an idea of why traffic may be high on that particular day.
- I've filtered out any hours during the year that have a combined total of less than 300 cars per hour, as listing every hour for the entire year would make the graphs unreadable, and I'm too lazy to figure out some neat-o online graphing tool that would let you input a date and get a graph in return. I'm not sure if 300 cars per hour is a good mark or not, it's kind of an arbitrary guess based on the data and my experience.
- As you might expect, the busiest times tend to be Sunday afternoons, any last-day of a holiday weekend, and weekends during ski season when people are either heading up, or returning from Stevens.
- You may be thinking "Great - I'll just find a point on the graph where the volumes go below 300 vehicles per hour, and plan to pass through Skykomish at that time". I'd be happy if it were that simple, but it's probably not. Why? Mostly because I don't know if "peak volumes" actually equate to slow traffic. For example, if we look at an hour where 500 cars travel Westbound through Skykomish, that hour would appear on the graph and I'd assume that probably meant there was slow traffic during that time. However, what if all those 500 cars zoomed through Skykomish at 55 MPH because traffic was flowing smoothly? And further, maybe as soon as that peak traffic reached Sultan, the backup started, and less than 300 vehicles per hour passed through Skykomish in subsequent hours because they were all sitting stopped for minutes at a time in heavy traffic. At first glance, one would assume that less than 300 vehicles per hour = no traffic, but it just may not be the case. If any traffic experts out there have any educated thoughts on this (and actually happen to read this), I'd be interested in their opinions.
- On the graphs, East = Eastbound traffic, and West = Westbound traffic.
- On the graphs, the hours listed cover from the start of the listed hour to the end. So 0800 = traffic measured between 8:00 and 8:59 am.
January
February
March
April(Spring Break dates listed here were for Seattle Schools)
May
June
July
August
September
October
November
December
1 comment:
This is amazingly useful information for those of us who use the traffic corridor, but don't live near it.
However, the provisos that you give about flow and number of vehicles not being the same thing as "no traffic" were very well taken.
I am appreciative to add data to my intuition as I plan my trips! Thanks for the labor!
Nancy
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