I-5, like much of the Interstate system, is low on charm and high on practicality. It’s how Oregon guzzles gas and gets around.

Imagine Oregon as a 3 by 5 card. Interstate 5 runs like a vertical margin up and down the card, about an inch from the lefthand side. It connects Portland at the top to California at the bottom, and in the middle runs for nearly half its length through the fertile Willamette Valley.

I-5 is 308 miles long in Oregon and has three sections. In the north, it’s urban freeway from Portland down to somewhere north of Salem. The mid section goes through all that flat valley farmland; a favorite way to pass the time here is count hawks on the fence posts. From Cottage Grove south it runs through increasingly mountainous landscape, until just south of Ashland it crosses the 4,000-foot Siskiyou Mountains, which can be tough going in winter — if the freeway there is open at all.

Rest stops, generally clean and safe, are located about every 30 miles.

Here are some mile markers to help you figure it all out (some places, of course, have more than one exit):

• 302 Portland
• 256 Salem
• 195 Eugene
• 174 Cottage Grove
• 125 Roseburg
• 58 Grants Pass
• 30 Medford
• 19 Ashland
• 3 Siskiyou Summit
• 0 California

For road conditions anywhere in Oregon — including helpful webcam views — try tripcheck.com.