Do You Remember The "Magic" Speed Limit Signs???

[thenetwork]

As a kid, living in Ohio in the 70's, there used to be speed limit signs on state highways (mostly on rural stretches) that would read a different speed limit, depending on the time of day.

For example, these "Magic Signs" could read 55 for the speed limit in the daytime, and 50 at night.  If you watched the sign at night, you could sometimes see the sign change from 50 to 55 right before you passed it.

ISTR the Ohio State Driver's Handbooks/Rules would have an example of this type of sign in the common road signs section.

1) Anybody remember this type of sign? 
2) Was it just limited to Ohio?
3) How did they put the "magic" in these signs?
4) When were they eliminated?  (It sounds like, despite it being a unique little innovation, it was ultimately pooh-poohed by ASHTA).

[agentsteel53]

I know Florida used them, and I think there was one in place just over the border in the early 2000s.

http://www.alpsroads.net/roads/fl/i-95/sl.jpg Alps' Roads dislikes hotlinking.

here's an example from Michael Summa.  (the photo is from 1982, but the sign is at least 8 years older ... speed limits above 55 were abolished in 1973-74)

[J N Winkler]

Washington State used them too.  A friend was able to get a copy of the sign detail drawing from WSDOT for me a few years ago.

[mightyace]

I don't remember them in Ohio, but back then, we always crossed Ohio in the daytime.

But, how did this type of sign work?  What was the "magic?"

[realjd]

I know Florida used them, and I think there was one in place just over the border in the early 2000s.

Currently in the locations where the night speed limit is lower than the day speed limit (Big Pine Key along US1 comes to mind), the day limit is non-reflective so in the dark all that shows up is the night limit (white on black). I don't know if I'd call that magic however...

[agentsteel53]

But, how did this type of sign work?  What was the "magic?"

in the daytime, white shows up as white, while black shows up as black.

at night, retroreflective shows up as white, while non-retroreflective shows up as black.

so, through judicious use of four different combinations, including non-reflective white and retroreflective black, you can make a sign with two entirely different messages depending on whether it's day or night.

I would imagine the easiest way to do this is with two screens - first, screen-print non-reflective black, on non-reflective white.  Then, using a second design, screen-print glass-bead ink over the result, thereby setting the retroreflective bit.

[wh15395]

I feel like this could be a good idea on interstate highways in the city. If cities or states feel the necessity to have a 55 MPH speed limit, couldn't we at least limit it to rush hour. Then during non-rush hour times there could be a 60 or 65 MPH speed limit.

[Brandon]

I feel like this could be a good idea on interstate highways in the city. If cities or states feel the necessity to have a 55 MPH speed limit, couldn't we at least limit it to rush hour. Then during non-rush hour times there could be a 60 or 65 MPH speed limit.

Why?  If I'm not standing still during my rush hour commute, I'm going 70-75 mph anyway.

[wh15395]

I feel like this could be a good idea on interstate highways in the city. If cities or states feel the necessity to have a 55 MPH speed limit, couldn't we at least limit it to rush hour. Then during non-rush hour times there could be a 60 or 65 MPH speed limit.

Why?  If I'm not standing still during my rush hour commute, I'm going 70-75 mph anyway.

True, but I was just saying that because the reason for the low speed limits is because of heavy traffic. I agree that it should be at least 65MPH all the time, probably higher.

[Fixed quoting mishap. -S.]

[AZDude]

A number of miles on I-90 outside Seattle uses them.

[JREwing78]

Michigan used them as well before the 55mph speed limits went into effect in 1974.

[ATLRedSoxFan]

Georgia used to have them up until the mid 70's

[mightyace]

Michigan used them as well before the 55mph speed limits went into effect in 1974.

From what everyone has said, it looks like most of the old ones died in 1974 with the 55mph limit.

[averill]

Boy do I !!! 

I have the old Florida tech. drawings to make those "reversible day/night" speed limit signs, and have made a few myself.  As stated, a combination of non-reflective white for the night speed and reflective black (it reflects white at night.)  I would love to obtain one or two of the originals from the pre 55 days.  But only Mike and a few others have any.

N. Carolina, Georgia, Tennessee, Ohio, Florida used them (S. Carolina might have used them).  Other states used the more usual black "NIGHT" tab under the std. day speed sign with the day speed on a non-reflective white background.

I love what "Thenetwork" said "For example, these "Magic Signs" could read 55 for the speed limit in the daytime, and 50 at night.  If you watched the sign at night, you could sometimes see the sign change from 50 to 55 right before you passed it."  I remember those times as a kid, too, when we would drive to Florida for Christmas Vacation and notice the same thing.   As for AASHTO, who cares what they think.  The signs worked very well.  There is no innovation in traffic engineering any more because of associations like AASHTO, ITE (which I'm a member,) etc. only for the "so called” sake of complete uniformity!  I'm so glad that I'm not the only one who noticed those reversible speed limit signs, and revered them!  God Bless you all!

Averill; alhecht@comcast.net
PS I make these at home using the spec. from the states.  I make full size and miniatures.

[Tom]

Before 1974, the signs in Michigan would read 65 m.p.h. in the daytime and 55 m.p.h. at night.

[N9JIG]

Doesn't Texas still use these on Interstates? I thought these were what I saw on I-40 last week, with 70 during the day and 65 at night. Since I went thru there during daylight this trip I couldn't tell if the black night portion were retro-reflective or not.

[agentsteel53]

Doesn't Texas still use these on Interstates? I thought these were what I saw on I-40 last week, with 70 during the day and 65 at night. Since I went thru there during daylight this trip I couldn't tell if the black night portion were retro-reflective or not.

no, the magic signs are a single sign with a single number field, as opposed to separate day and night numbers. 

I offhand do not remember if the day speed limit signs are retroreflective in Texas.

[Zmapper]

I think I saw one on I-70 WB between Colfax and C-470 in Denver before. I don't know if it is still there or not.

[SteveG1988]

The NJ Turnpike has signs that uses Vane Type tech for display.
http://en.wikipedia.org/wiki/Vane_display
Do not know if this is 100% the same, but they do change it depending on traffic

[thenetwork]

I think I saw one on I-70 WB between Colfax and C-470 in Denver before. I don't know if it is still there or not.

You might be referring to the 2-year-old LED variable speed limit signs that were installed in that area (all the way west to Vail on I-70).  Heck of a lot easier to read than the earlier generation variable speed limit signs which used light bulbs behind day-glo flippy elements.

[averill]

Doesn't Texas still use these on Interstates? I thought these were what I saw on I-40 last week, with 70 during the day and 65 at night. Since I went thru there during daylight this trip I couldn't tell if the black night portion were retro-reflective or not.

no, the magic signs are a single sign with a single number field, as opposed to separate day and night numbers. 

I offhand do not remember if the day speed limit signs are retroreflective in Texas.

NO.  Back before the 55 Texas used "exposed glass beads" spread on the white paint "SPEED LIMIT" top portion of the sign, and plain white paint were the "70" was placed, so the day speed would not show at night.  Below was placed the std. white text on a black background.  The two sign concept.  Averill alhecht@comcast.net

[averill]

Someone on E-Bay is selling an old Missouri 65 sign that looks like it has this magic combination.  I just don't have the money right now.  Plus I have made some of these myself!  If you're interested type "highway signs" and scroll until you find it.

[vtk]

One of my parents told me about those signs once.  Apparently vandals sometimes bent the signposts to funny angles, somehow making the day.speed limit display at night.

Retroreflective black sounds like an oxymoron, but it's actually charcoal gray, not black.  The vans I drive at work have their numbers in retroreflective charcoal gray; the rest of the van is of course nonreflective white.  At certain headlight distances, this combination is unreadible because the retroreflected dark gray is the same brightness as the diffused white.

[averill]

I made a night time rendering of Mike Sumas's speed limit sign as it would look at night, I will try to post the picture on here somehow, if someone knows how to do it, please write.  Averill

[Scott5114]

I made a night time rendering of Mike Sumas's speed limit sign as it would look at night, I will try to post the picture on here somehow, if someone knows how to do it, please write.  Averill

Post it online somewhere first (Imgur is pretty simple to use). Then, click "Reply", click , and place the link to the image between the tags that button creates.