Q: My question is about speed limit signs. When I see the sign does it mean I go that speed now or when I get to the sign?

A: When a speed limit changes, the new speed limit takes effect at the location of the sign. If the speed limit is increasing don’t speed up until you reach the sign, and if the speed limit is decreasing slow down before you reach it.

The Manual of Uniform Traffic Control Devices states that speed limit signs “shall be located at the points of change from one speed limit to another.” Since Washington has adopted the MUTCD as law I thought that was it. It wasn’t. Washington made a few modifications.

The revision didn’t include anything about sign locations. I haven’t found a reference to give you for a single law or regulation that specifies where a speed limit sign goes, but I can give you a whole bunch, starting at the state level. The Department of Transportation Traffic Manual specifies that speed limit signs be installed “at the location where a speed limit changes to another.”

Locally, your city or county likely has a similar rule. In the county where I live, the county code says that all speed zones “shall be properly signposted at the extremities thereof.” Despite the odd language, you get the point.

What about when the speed limit signs in opposing directions don’t line up? Did the people installing the signs violate the law? Is there a gap where the speed limit is unknown? I’m not sure how frequently that happens; I took a look at three speed zone changes near my house, and in two of the three the signs on both sides of the street were directly across from each other.

In the other instance, they were offset by about 50 feet, but if they’d been lined up perfectly someone would have had a speed limit sign in their driveway.

The law that requires road users to obey traffic control devices has a phrase about signs “placed in position approximately conforming to the requirements,” suggesting that there’s some wiggle room for sign placement.

Often when people ask questions about speed limits, there’s an underlying theme of, “How much can I get away with?” But for drivers who wonder that, let me propose a counter-question: “What can I do to make our roadways better for everyone?”

Even though most drivers travel at or within just a few mph of the speed limit, speed is a factor in 31% of fatal crashes in Washington. Slowing down makes a big difference in the safety of other road users, especially walkers and cyclists.

Many of you do great things in your communities–coach a kid’s team, volunteer at a food bank, teach someone to read–here’s another one that’s easy once you practice: if you don’t do it already, make “follows the speed limit” one of the good things you do for the world.

Doug Dahl writes “The Wise Drive” weekly column for this newspaper. He’s with the state Traffic Safety Commission.