On the topic of traffic engineering, I have a pet peeve with California. Why don't highways have exit numbers? This can result in problems like two exits on I-880 in the East Bay area being for Fremont Blvd about 10 miles apart. And if I miss an exit, how do I know if I have missed it? That's so easy with numbers.

1. I also grew up in DC. The worst signage for me is getting on the 14th st. bridge from DC. At a certain point, you have to take a turn labeled Jefferson Memorial (there may be a tiny sign saying Virginia but I have never seen it). Since I rarely went to Va when I was growing up, I did not know this trick and only found out when I had another native in my car.

2. The problem with exit numbers seems to be a bad choice way back. Sequential numbers are unsatisfactory because they make it hard to add or remove exits (the NJ turnpike has exits like 14a etc. for this reason). The solution that works best is labeling the exit with the closest milepost number. This is an absolute, and has the advantage that it tells you the distance between exits. (You still occasionally have more that one exit with the same number, in cities typically, but that is not too big a deal.)

But here is where the California decision way back comes in. In CA, mileposts are county based, not state based, so they reset when you cross a county line. Numbering exist with county miles would result in multiple exits with the same num\bers. They could number exits with the true state mileage, but that would cause confusion in emergencies ("we need an ambulance at milepost 100 on 101N" -- is that near exit 100 or county milepost 100?). Re-mileposting seems a hopeless task (every brige etc. is labeled with its county milepost and all would have ot be changed, making old records confusing).

The Defense Mapping Agency got aglomorated with some imagery and CIA groups in 1996 and are now the National Imagery and Mapping Agency.

Time to update those signs...

-Kurt

Exit numbers in California -- check out the link. Maybe now that there is a budget it might happen!

Looking at it...on I10, exits 1b-10 have been installed. 27 have been installed in various parts of I5, including grand old Exit #796 (mileage based), Hilt Road at the Oregon border.

However, there cannot be much more confusing than getting off the Bay Bridge and hitting 80 East and 580 West. The same road. The same direction. Heading North!

"495 - Maryland"
It sounds like you ran into one of those new "Evacuation Route" signs that DC started putting up in responce to Nine-Eleven. (Let's see if I can insert an HTML link in this post -- The related article is here -- Subtle Signs will Show the Way. If that didn't work, just click my name. ).

For whatever bizarre reason, they didn't want to mark these as "evacuation routes" but as "to Interstate 495", therefore ignoring the other major highways out of the city that people might wish to use -- Interstates 66, 95, 395, 270 and US Routes 1, 29, and 50. I would believe it would be more helpful if signs directed to PG county said "to I-95/495" while signs directed to Montgomery county said "to I-495" or "to I-495/270"

Of course, if you understand the signs to be evacuation routes, opposed to normal guide signs, you'd now have the idea why it doesn't send people back into Georgetown. If you're trying to get as many people out of the city as quickly as possible, you don't want to direct them back into downtown.

Of course, now you can ask the obvious question: "If the signs are intended for when they have to evacuate the city, why isn't it assumed that Canal Road would be set up to be one-way outbound?"

I've always wondered why D.C. (where I too grew up) doesn't implement numbered highways for main routes--except on the large maps in the Metro Stations. (Check it out, upper Conn Ave is labeled 185, just like it is in Maryland!)

Who else remembers when D.C.'s federal highway markers (the shields), most of which have unfortunately been taken down all over the USA, were color-coded? By compass point, IIRC.

My favorite example is the "Intersection of Death":

If you come across the Roosevelt Bridge from VA, and make the first possible right-hand turn, you abruply find yourself at the dead end of a 6 lane highway (25th St.), at a stop sign. And if you then want to turn left, you have to scoot across the oncoming traffic of the NorthWest-bound lanes of the Rock Creek and Potomac Parkway.