Author: DOUG DAHL

Q: When we drive our 45-foot motorhome on the freeway, are we supposed to be going the car speed limit or the truck speed limit?

A: The truck speed limit sign is a little misleading; or if not misleading, at least incomplete. Of course, it’s impossible to put the full RCW up on a street sign so I suppose it’s the best option we’ve got. When you see a speed limit sign that says, “Speed Limit 70, Trucks 60,” the word “trucks” is a stand-in for more than just trucks.

Q: The back of transit buses have a flashing yellow light and a “Please Yield” sign, so I yield for them when they are pulling out of bus stops, but I see that many drivers do not. Is the “Please Yield” a request for drivers to be polite, or is it the law?

A: You don’t see a lot of “please” in the legal code, do you? For the parents reading this, have you used please in a sentence when your child didn’t have the option of refusing? Like, you say, “Please clean your room,” but what you mean is, “You will clean your room, or I’m not driving you to Ben’s birthday party, and there’s going to be a bouncy house there.” You say please because you want your kid to like you, but you still have an expected behavior and a consequence for disregarding it.

Q: Sometimes while driving on a freeway with three or more lanes I’ll see another driver change two or more lanes at once. I was under the impression that you’re only supposed to change one lane at a time. Is it legal to do a multi-lane change?

A: I don’t really want to answer this question, because I’m concerned about how some drivers might alter their driving habits for the worse. However, if you’re reading a column on traffic safety I’m going to trust that you’re not who we need to worry about.

Q: I was reading about how a lack of sleep affects our brain, and it got me wondering how it affects our driving. What kind of data are there around drowsy driving?

A: As I write this it’s the Monday after setting the clocks forward an hour. I feel like I started my day a half-hour ahead of schedule, but I’m actually behind. I could go on a tangent about the loss of productivity and actual physical harms caused by daylight savings, but since you’ve been reading about the problems associated with a lack of sleep you probably already know that.

Falling asleep while driving is obviously a problem. I don’t think that needs any explanation. Even if you’re at the point of rolling down the window and turning up the stereo to prevent nodding off, we have a safety issue. If you’ve convinced yourself that closing one eye at a time while you drive is a reasonable solution to your exhaustion, well, it’s not; you’re not a dolphin. But you are sleep deprived. (Nature trivia – dolphins can sleep with one eye open. They rest half their brain at a time so they can watch out for predators and come up for air.)

Q: I have noticed a high number of cars and trucks without their lights on in bad weather. But here’s the thing – about 75 percent of them are black, dark blue, dark gray – the color of wet asphalt. I’m clueless about why people with dark-to-black cars see no need to turn their headlights on, especially close to sunset on rainy days. I often don’t see them coming from behind. Any ideas?

A: I just stepped out of my office and took a look at the cars parked along my street. Of the 25 cars I can see, 16 are black, gray or silver. That’s higher than national studies showing that these colors make up around 52-55 percent of vehicles on the road. If our choice of car color is correlated with the clothing color choices for the typical Washingtonian, that makes sense.

Q: At an intersection with a red light camera, what is the period of time required by the camera to be considered a complete stop before making a right turn on a red light?

A: There’s a story behind this question, isn’t there? Did anyone else read that question and think to themselves, “Someone just got a ticket.” That’s way too specific of a question to be just a curiosity.

A red light camera is, at its core, sensors, cameras and a computer. The sensors, installed in the pavement, measure the movement of cars through the intersection. When the traffic signal is green the computer ignores the messages from the sensors. When the light is red, the computer listens to the messages from the sensors. If the sensor says, “hey computer, this car is still moving,” the computer tells the camera to take a couple pictures of the car. An officer then reviews the data to confirm a violation has occurred. The people who design these systems might tell you it’s more involved than that, but you didn’t ask an engineer.