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[cbalducc]

I remember going on vacation to the Great Smoky Mountains with my family in 1984.  I remember seeing ginormous speed limit signs between the east and westbound lanes on I-40 as we drove in the border area of Tennessee and North Carolina.  They were encased in black boxes, which led me to think they may have been backlit to be seen at night.  Does anyone else recall similar signs?  God bless.

[OracleUsr]

Those "Black box" speed limit signs were convertible.  If fog appeared, the lights at the top would flash and a panel would flip up and say "FOG 35" instead of "55"  I don't think they were ever backlit otherwise.

[realjd]

Cool! Does anyone have any pictures?

EDIT: fix stupid iPad autocorrect

[OracleUsr]

I wish I did

[roadman65]

NJ has been using changeable speed limit signs for years.  Alpsroads, I think, has pictures of what they look like.  I-4 now has them from US 17. 92. and 441 to Lee Road (SR 423) in Orlando and drops the speed limit from 50 to 40 when accidents occur.

[DeaconG]

I-495 in Delaware has them, although the few times I drove that road I never saw the speed change.

[MASTERNC]

I-495 in Delaware has them, although the few times I drove that road I never saw the speed change.

I've seen them changed due to weather, air quality, or construction.

[Steve]

NJ Turnpike still uses them, though the new ones are larger and more modern (and hopefully work). Also, US 1/9/Pulaski Skyway has some older ones. That's all I can think of in this state.

[1995hoo]

For a few years there were lighted variable speed limit signs on the Capital Beltway in Virginia between the Springfield Interchange and the Woodrow Wilson Bridge as part of the ongoing road construction project, but they were removed sometime either last year or the year before. A Washington Post report said that the funding for the variable speed limit experiment had run out. As a practical matter, drivers ignored the variable speed limits anyway and drove as they normally would.

I believe they first posted them in the summer of 2008, because I recall the first time I saw them in use was when I was returning home from a trip to Nova Scotia.

[bassoon1986]

kind of like the speed limit signs on Mobile Bay Bridge on I-10 or Atchafalaya Swamp I-10 in Louisiana

[roadman65]

The Chesapeake Bay Bridge Tunnel used to have changing signs that were not digital, but had 4 lenes on them for 4 different speed limits.  55 was in a green signal type of lens and the lower speeds had yellow, I guess it makes sense to have a caution for a speed that is reduced for weather or accident.  Since it was dualized, fixed speed limit signs were added.

[OCGuy81]

I posted this in General Highway Talk as well under Best of Road Signs.  These are seen in Seattle.  Was this similar to the old speed limit signs you might have seen?

[Truvelo]

I'm not sure if the original post was referring to purely backlit signs or those which are capable of showing variable speed limits. Over here we have both types. If a road has street lighting the signs must be illuminated at night whether backlit or a traditional reflective sign with a light shining on it. Below are some pictures of backlit signs at the point a speed limit changes from 30 to 40. It is the normal thing over here to have a single sign with a speed limit roundel on each side.

We also have variable speed limits which use matrix signs like the Seattle example posted above. Ours must have a red ring round them to be lawful, if not the limit is just advisory and not enforceable. Ours are also capable of displaying a different limit for each lane, maybe the Seattle ones do as well?

[deathtopumpkins]

Ours are also capable of displaying a different limit for each lane, maybe the Seattle ones do as well?

I doubt it, I'm reasonably sure that having different speed limits between contiguous lanes is not legal in the US.

[J N Winkler]

I doubt it, I'm reasonably sure that having different speed limits between contiguous lanes is not legal in the US.

I don't think there is anything in the MUTCD that actually prohibits them, and there are some examples of fixed permanent speed limits which vary lane by lane.  On I-70 ascending the mountains out of Denver, for example, there is a minimum speed of 50 MPH in the left-hand lane.  Back in the 1960's California experimented with permanent lane-by-lane speed limits:  the objective was to see if lane discipline would improve if the passing lanes had higher speed limits than the driving lanes.  It did not.

[vtk]

There are a few school zones around here that use partially lit signs.  They look much like standard SL signs, except there's a flourescent yellow-green "SCHOOL" banner on top, and the number is done a little differently.  In a hole cut in the sign is mounted a hooded light display which, when on, shows "20" in white (or possibly yellow-green) on black.  It looks like the number is made of LEDs, but given the age of the signs, it might be incandescent light shining through holes in a black mask. Sometimes there are also yellow lights above and below the sign which flash when the speed zone is in effect.

[US71]

School Zone in Marshall, MO



"NAG" sign in Marshall, TX

[xcellntbuy]

There are a pair of similarly lighted electronic speed limit (supposed to be 65 mph) signs in the northbound lanes of the Sawgrass Expressway (FL 869) north of the Sample Road exit and before the "big curve" bending to the east.  They may exist southbound as well, but I rarely travel in that direction on that toll road.

[bulkyorled]

These seem to be becoming increasingly popular in at least a couple areas near me. Glendale & Burbank have several sets of speed limit signs that are LED lit. Not the "Your Speed" type as shown above but flat out Speed Limit signs. I can fetch a picture sometime of one since I can't quite recall where they are exactly

[KEK Inc.]

I posted this in General Highway Talk as well under Best of Road Signs.  These are seen in Seattle.  Was this similar to the old speed limit signs you might have seen?

That's a mock-up WSDOT cocked up on a computer.  Here's a live picture:  

(Personal Image)

They actually use the FHWA fonts.  These signs also have another purpose.

(WSDOT Image)


(WSDOT Image)

[Central Avenue]

Interesting how they were very careful to match the FHWA series for the speed limit display, but the "MERGE" lettering is in a more typical VMS font.

[D-Dey65]

I still remember traffic signals being used as speed limit signs along the Chesapeake Bay Bridge-Tunnel. I wish I could find proof of them.

[bulkyorled]

I posted this in General Highway Talk as well under Best of Road Signs.  These are seen in Seattle.  Was this similar to the old speed limit signs you might have seen?

That's a mock-up WSDOT cocked up on a computer.  Here's a live picture: 

(Personal Image)

They actually use the FHWA fonts.  These signs also have another purpose.

(WSDOT Image)


(WSDOT Image)

Those are actually pretty cool. I wish we had some of those here...

[KEK Inc.]

They're not cheap...









It costed the state $113 million to install about 6 gantries with these bad boys on I-5, and an extra $42 million for 4 gantries on SR-520. 

[agentsteel53]

It costed the state $113 million to install about 6 gantries with these bad boys on I-5, and an extra $42 million for 4 gantries on SR-520. 

that seems about an order of magnitude high.  what is the cost breakdown?  42 for 4 implies 10 million per gantry.  call the post and the wiring about 100000, so almost 10 million for 6 signs.  maybe 1.5million per sign?  that seems way high.