Perhaps it's because so many of WGBH Radio listeners are tuning in while driving that the Curiosity Desk inbox and Twitter feed is reliably filled with roadway related questions. Well, today we attempt the unprecedented: Answering three of them in one fell swoop. And since all of them have to do with road related signs, I decided to take a road trip. A quest of sorts to not just find them all — but also find some answers.

And Nine-Tenths Of A Cent

As I gassed up my trusty, manual transmission 2007 Toyota Yaris, I was already in the perfect position to find my first sign on the list: A big placard letting me know how much I was paying for gas. Quite clear was the $3.09 cost per gallon. Less visible was the additional nine-tenths of a cent I was paying. This is of course standard practice at the pump, and something that caught twitter user @jalbertj's eye.

"Well basically, in short, the answer is taxes," explained Ed Jacobson, who used to own a slew of gas stations and today runs the Northwoods Petroleum Museum in Wisconsin.

It was in the 1930s, during the Great Depression, that the federal government issued its first gas tax — a penny a gallon — which was easy to simply pass on to the consumer. But when the tax was raised to 1.5 cents per gallon in the mid-1930s, that posed a problem.

"So, the oil companies figured out a way to reconfigure the pumps," said Jacobson. "So they could calculate in half a cent."

The pumps were mechanical in those days, and with the simple adjustment of a pin, that half a cent could be kicked all the way up to nine-tenths of a cent. Not surprisingly, this quickly became standard practice.

"That nine-tenths of a cent has become a marketing tool, as you can probably imagine," said Jacobson. "Instead of saying $3 a gallon you say $2.99."

And don’t expect it to go away any time soon. Jacobson says all those nine-tenths of a penny add up to more than $2,000 a month at the average station. And stations that have experimented with eliminating it for simplicity have consistently lost money. Jacobson also pointed out that gas stations aren't alone in doing this. Property tax and state sales tax are also typically calculated at a percentage of a cent (Massachusetts sales tax in hundredths of a cent at 6.25 percent). They simply don't have big signs everywhere to remind you.

Why Not Just Say 30 Miles Per Hour?

Once in the car, I headed out of the city in search of sign number two, one that caught the eye of Worcester resident Larry Baitch, a recent transplant from Texas.

"My wife and I have taken a number of daytrips and been puzzled by sings that we have seen in certain small towns and hamlets — and the signs say Thickly Settled."

Well Larry is right that these appear mainly on rural roads, when they hit a more populated stretch. In my search for just such a sign, I made my way out past Concord, then traveled back toward the city, south on 62 and then east on 117. As the placid woods gave way to Waltham, I hit pay dirt — a classic yellow, diamond-shaped sign with the words in bold black caps: THICKLY SETTLED.

Nobody was able to give me a definitive answer as to its origins beyond speculating that it’s just a classic, quaint New England turn of phrase. But what is no mystery is its meaning, strictly defined in the Massachusetts General Laws, Chapter 90, Section 1.

"...the territory contiguous to any way where dwelling houses are situated at such distances as will average less than two hundred feet between them for a distance of a quarter of a mile or over. "

Crucially the law also mandates that drivers must travel at a “reasonable and proper” speed, which in a thickly settled zone — even when not posted — means 30 miles per hour or less.

Color, Color Everywhere — Small Signs To Make You Think

Finally, I left the byways for the highways to spot a collection of mysterious little signs that Bruce Gillard sees during his regular trips from Cranston, Rhode Island to New Hampshire and back.

"When I'm driving on the highway I see these little rectangular signs on the side of the road. They're all about the same size. They're white, they're red, they're green, some are yellow. And I'm just curious why they're there. "

These colored rectangles have a name: highway delineators. The red and green ones are related. Red at the start and green at the end of every guard rail. Given what we are well trained to do when we see the colors red and green on a roadway, this color scheme seemed backwards to me until I learned who these signs are really aimed at.

"So, they’re meant to be sticking out of the snow if we have a deep snow pack," explained Charles St. Martin with the Rhode Island DOT. "So as the plow drivers are going along they know exactly where that object is in case it’s covered by snow."

The red and green delineators are all over Massachusetts and Rhode Island highways, but as I traveled Routes 93 and 95 in Massachusetts, I was having a hard time finding more than the occasional white or yellow one. Then I crossed into Rhode Island. Here, they were consistently spaced along both sides of 95, yellow ones on the left and white ones on the right. As St. Martin explained, the colors correspond to the lines painted on the road.

"You traditionally see a double yellow [line] on your left, and white line on the right," he explained.

These delineators are reflective, and were installed throughout Rhode Island a few years back. Their purpose? "To increase visibility for older drivers as well as during snow events or rain events when it might be a little harder to see the striping on the road," said St. Martin.

And a pro-tip for Rhode Island drivers. Some of those white delineators have a single black horizontal stripe through them. Those appear just before and after exits and on ramps, where you can expect merging traffic.

My thanks to @jalbertj, Larry and Bruce for their questions that led to today’s story, What’s yours? Email me at curiositydesk@wgbh.org.