"Keep min 2 dots apart" signs?

[noelbotevera]

On US 322 between PA 45 and PA 144, there are three sections of road where dots appear. Signs that say "Keep min 2 dots apart" are posted on the three sections.

Here's an example of one of the signs.

Have these been used anywhere else, or is it a PA exclusive? Also, do these dots have a name?

I think this must have been a high accident area of US 322 (we saw skid marks along one of the dotted sections), and PennDOT must have experimented with these a couple years ago (the paint is fairly new, and the signs are Clearview - the GSV shows 2012).

The strange thing is that the dots have no warning of them ending. Basically they just suddenly disappear, and the next sign that tries to warn you about following distance is this, this, and this, at the next dotted section.

[slorydn1]

Those dots probably represent 1 second of travel time at the posted speed limit for that road, so 2 dots would equal the 2 second gap we are supposed to leave between us and the vehicle in front of us.

[jemacedo9]

Those yellow signs are in several places across PA...but the white dots I've only seen in two other places in PA:  PA 147 between where the freeway ends and Northumberland, and I THINK on I-80 in the East Stroudsburg area.  If they're not on I-80 now, I feel like they were there maybe 10 years ago?

I've never seen the dots in any of my travels outside of PA.

[slorydn1]

Those yellow signs are in several places across PA...but the white dots I've only seen in two other places in PA:  PA 147 between where the freeway ends and Northumberland, and I THINK on I-80 in the East Stroudsburg area.  If they're not on I-80 now, I feel like they were there maybe 10 years ago?

I've never seen the dots in any of my travels outside of PA.

I've never seen anything like that myself, I am just guessing at this point (though it would make sense). I haven't been to PA myself since 1987 if memory serves.

[jeffandnicole]

There's no ending sign because you're never supposed to tailgate. In theory, it has helped you determine how far apart you should always be behind the car in front of you.  There's no end point in when you're allowed to tailgate again.

[noelbotevera]

The problem comes when people do tailgate. You have conga lines of four or more cars abutting each other, and they're less than half a dot away. That's equivalent to about half a second or so away (the speed limit for this stretch here is 55 mph).

[Zeffy]

The problem comes when people do tailgate. You have conga lines of four or more cars abutting each other, and they're less than half a dot away. That's equivalent to about half a second or so away (the speed limit for this stretch here is 55 mph).

I like to remain fairly distant from the vehicle ahead of me. Anyone who tailgates me generally finds that if they don't back off I'll drive slower just to piss them off.

[Kacie Jane]

They're not there anymore, but at one point (I'm guessing about 10 years ago, but I'm pulling that number out of my you know where), I-5 north of Olympia had them.

[1995hoo]

I seem to recall some conceptually-similar signs on the eastbound M4 somewhere east of Bristol (England) with a scheme that used chevrons instead of dots.


Edited to add a picture I found, though I don't know which motorway this is:

[74/171FAN]

Those dots probably represent 1 second of travel time at the posted speed limit for that road, so 2 dots would equal the 2 second gap we are supposed to leave between us and the vehicle in front of us.

Information on this is on page 5-91 in PENNDOT Publication 638(District Highway Safety Guidance Manual).

The major information is placed below, I have not seen or heard of anything like this to this point but it seems to be a possible way of implementing low-cost safety improvements on two or three-lane roads.

Markings are spaced such that safe distance is kept between vehicles when a minimum of two markings separates them. Safe distance is defined based on a 2 second following rule.

[hbelkins]

I've seen them on PA 322 in the State College area and on I-80. I guess the combination of pavement markings and regulatory signs can give police cause to pull over drivers who follow too closely.

[Roadgeek Adam]

I've seen them on PA 322 in the State College area and on I-80. I guess the combination of pavement markings and regulatory signs can give police cause to pull over drivers who follow too closely.

I need not explain what's wrong with this sentence.


As for the topic at hand, the ones on I-80 I've known for a long time. I loved them as a kid, because they were so unusual to me at least.

[cu2010]

I seem to recall some conceptually-similar signs on the eastbound M4 somewhere east of Bristol (England) with a scheme that used chevrons instead of dots.

Ontario used to have them on the 401 at one point, though they are no longer in use.

[jakeroot]

This should probably go in traffic control.

I seem to recall some conceptually-similar signs on the eastbound M4 somewhere east of Bristol (England) with a scheme that used chevrons instead of dots.

Can't remember which motorway (hell, it could have been an A-road), but the UK's implementation was my first experience with "keep apart" signs. I'm glad to see them making their way over here. However, British motorists are quite a lot more disciplined than we are, so I'm uncertain as to how effective these dots will end up being, this side of the pond.

[Bitmapped]

There used to be a set on former US 220 around Port Matilda, PA but I think they were gone last time I was through. After the traffic moved to I-99, I suspect PennDOT decided they weren't worth maintaining anymore.

[1995hoo]

This should probably go in traffic control.

I seem to recall some conceptually-similar signs on the eastbound M4 somewhere east of Bristol (England) with a scheme that used chevrons instead of dots.

Can't remember which motorway (hell, it could have been an A-road), but the UK's implementation was my first experience with "keep apart" signs. I'm glad to see them making their way over here. However, British motorists are quite a lot more disciplined than we are, so I'm uncertain as to how effective these dots will end up being, this side of the pond.

Funny thing is, I seem to remember that when I took driver's ed they advocated a two-second following distance under 40 mph and a four-second distance over 40 mph. I've tried counting off what a four-second distance would be and it's HUGE. It'd be pretty much impossible to maintain that distance on most urban or suburban highways I travel because people would cut into the gap. Even a two-second distance is probably farther than most people perceive when they think about what distance is safe, although that's no excuse for following too closely. (Out on rural non-Interstates it doesn't much matter either way due to lack of traffic.)

Semi-related to this topic: When I read car reviews that mention adaptive cruise control where the car adjusts the following distance to keep a safe space, I've often wondered if such systems can be essentially counterproductive on highways with relatively high traffic volumes and aggressive drivers because even with a two-second distance, somebody's going to cut into that gap, and I assume that means the adaptive cruise will back off the speed to re-create a two-second gap, which in turn is an invitation for another driver to cut in, etc....eventually the car backs it off so far that you're not getting anywhere. Or am I missing something? (Aside from the sensible driver not using the system in that kind of traffic, of course.)

[AsphaltPlanet]

I seem to recall some conceptually-similar signs on the eastbound M4 somewhere east of Bristol (England) with a scheme that used chevrons instead of dots.

Ontario used to have them on the 401 at one point, though they are no longer in use.

I don`t have a picture of the signs, but here are some of the remaindered chevrons on the 401 through Whitby.

http://asphaltplanet.ca/ON/hwy_401_images/401_cl_409_east_May05_lg.jpg
http://www.asphaltplanet.ca/ON/hwy_401_images/Hwy401_p11_images.htm

The 400 also had some through King Township in York Region:
http://www.thekingshighway.ca/PHOTOS-4/hwy400-311_xlg.jpg
http://www.thekingshighway.ca/PHOTOS-4/hwy400-313_xlg.jpg
http://www.thekingshighway.ca/PHOTOS/Hwy400photos5.htm

[Kniwt]

It was tried in 2006 in Washington state and very quickly abandoned.
http://thenewspaper.com/rlc/news.asp?ID=1289

During heavy Saturday traffic, however, motorists maintained the 160-foot distance as required by the posted signs, even though such distances were unnecessary at the crawling pace. This further reduced the freeway's capacity causing a chain-reaction slow-down.

"The idea was not to impede traffic, but to increase safety," state Traffic Engineer Ted Trepanier said in a statement provided to The Olympian newspaper. "We apologize for delays drivers faced as a result of this program."

[jeffandnicole]

The problem comes when people do tailgate. You have conga lines of four or more cars abutting each other, and they're less than half a dot away. That's equivalent to about half a second or so away (the speed limit for this stretch here is 55 mph).

It's actually about a second at that point. 

The way it works is there's two dots.  Trying to explain it here, it works like this:

Car  Dot                     Dot  Car

As you see, there's a wide space between those two dots.  If a car was 1/2 second away, it'll look like this:

Car  Dot  Car               Dot   Car

But if a car was one second away, it'll look more like this:

Car  Dot        Car         Dot  Car

Another thing to do is count 'One Mississippi Two Mississippi' wth a fixed object or marking, such as a sign or line in the road.  You should be able to say One Mississippi with ease.  Obviously, it's better to say One Mississippi Two Mississippi, but honestly in the real world in heavy traffic that rarely happens.

I've seen them on PA 322 in the State College area and on I-80. I guess the combination of pavement markings and regulatory signs can give police cause to pull over drivers who follow too closely.

What's the specific law on tailgating or following too closely?  While your safety publications generally will say 2 or 3 seconds, many states don't actually have that written into law.

The problem comes when people do tailgate. You have conga lines of four or more cars abutting each other, and they're less than half a dot away. That's equivalent to about half a second or so away (the speed limit for this stretch here is 55 mph).

I like to remain fairly distant from the vehicle ahead of me. Anyone who tailgates me generally finds that if they don't back off I'll drive slower just to piss them off.

That's a form of aggressive driving.  No, not them.  You.  And you're not just pissing that next person off, but everyone behind them.  In the end, it aggravates everyone, and it doesn't solve anything.

[Alps]

Whenever I see the dots, I intentionally get closer to the car in front of me. Just like when I see "Buckle up! Next million miles!" I immediately unbuckle my safety belt. Screw you nanny signs.

[Mr_Northside]

Also, do these dots have a name?

I don't know about an "official" name, but I recall when these showed up in PA, reading the name "Bott's Dots" (I think 2 "t"'s in Bott)

[jakeroot]

Also, do these dots have a name?

I don't know about an "official" name, but I recall when these showed up in PA, reading the name "Bott's Dots" (I think 2 "t"'s in Bott)

Bott's Dots are the physical dots separating lanes, seen mainly in non-snowy climates (although versions exist that are protected from snowplows)...

Whenever I see the dots, I intentionally get closer to the car in front of me. Just like when I see "Buckle up! Next million miles!" I immediately unbuckle my safety belt. Screw you nanny signs.

[jeffandnicole]

Also, do these dots have a name?

I don't know about an "official" name, but I recall when these showed up in PA, reading the name "Bott's Dots" (I think 2 "t"'s in Bott)

Bott's Dots are the physical dots separating lanes, seen mainly in non-snowy climates (although versions exist that are protected from snowplows)...

Whenever I see the dots, I intentionally get closer to the car in front of me. Just like when I see "Buckle up! Next million miles!" I immediately unbuckle my safety belt. Screw you nanny signs.

The plowable version are simply called 'plowable reflectors'.

[PHLBOS]

Stretches of Route 41 between US 1 & 30 in Chester & Lancaster Counties have these as well.

[ixnay]

Stretches of Route 41 between US 1 & 30 in Chester & Lancaster Counties have these as well.

Including just west of PA 796 in Chesco, which is burned in my brain having negotiated that stretch numerous times on my way to my stepbrother's or to Reading.

ixnay