In short, it was an ugly day for an ugly bridge. The Teddy Roosevelt Bridge carries Interstate 66 across the Potomac River between Rosslyn in Northern Virginia and Washington DC. The Roosevelt Bridge opened in 1964 and at one end goes just over the edge of Theodore Roosevelt Island, which is an underappreciated Washington park accessible only by a footbridge. The bridge itself is low enough that the trees from the island bounce up against the bridge near the Virginia side. The bridge looks like an iron structure, with signs of rust, far from picturesque. Some have noted the irony of Teddy Roosevelt's island, maintained by the National Park Service as a natural park, having such a bridge going over it.
The TR Bridge is a little over a half mile long, very low, and with pretty narrow pedestrian walkways on both sides. We went on the south side. The combination of a narrow walkway and a very low, thigh-level barrier separating the vehicles from the pedestrians does not make for a relaxing stroll. And the barriers on the water side aren't all that high either, about just above waist level. So, as far as scariness rating is concerned, what the bridge gives in height, it makes up in cramped, unprotected walkway. I give it a scariness rating of 2 (out of 10) for height, 3 for length, and 7 for width (solidity of side barriers, nearness to edge, etc), making a sum of 12 out of a possible 30. Not so bad, but not so great. Here's a case where others might agree with me, especially those who don't like cars driving just about right next to them at near highway speed.
And not all days can be nice ones for a bridge trek. The morning was overcast with a shower that went through town, and the forecast was for improving conditions, so we were off. The rain had stopped until we made it up to the bridge, when it started to sprinkle, and then by the time we were in the middle of the bridge, it was a steady rain, with some mild gusty winds, and who brings umbrellas onto a bridge trek? We started from the DC side, made it most of the way across, reaching Roosevelt Island, then turned around. The rain stopped as we exited the bridge. There were no other pedestrians or bikers on the bridge; they could not have been missed. That bridge is not made for pedestrians. It doesn't really seem to leave pedestrians off anywhere useful on the Virginia side anyway.
Well, maybe we can give that bridge another chance on a better day. And maybe during rush hour to slow down traffic.
Teddy Roosevelt Bridge
Arlington Memorial Bridge
If you're looking for a manageable walk over a beautiful bridge with a lot of history on both sides, the Arlington Memorial Bridge is a perfect choice. The bridge, which was completed in 1932, crosses the Potomac River and essentially connects Arlington National Cemetery on the Virginia side with the Lincoln Memorial on the Washington, D.C. side. There are wide, 15 foot sidewalks on both sides of the bridge, very accommodating to walkers; there are even seats built into the marble railings. It's not a long bridge, coming in at around 0.4 miles. And it's a rather low bridge, yet with a nice view of the surrounding area. 
The railings on this bridge are about as solid as they come, a very important attribute. They are made of thick stone, and reach to about shoulder level. That seems to be just about the perfect combination to allow good viewing and yet provide a sense of security to the wary walker. This is the first bridge I've walked across where it almost seemed better to be near the edge -- there is no barrier whatsoever between the road and the sidewalk. Nonetheless, it is an urban bridge with relatively slow traffic.
For July in Washington, the weather was great for today's trek over the bridge, with a break in the recent east coast heat wave. We walked from the Virginia side to the D.C. side, with a the Lincoln Memorial in front of us. And turning around, we could see the Lee Mansion in the cemetery sticking out of the hills. They say the bridge is symbolic in that it connects the old North and South; apparently Robert E. Lee wrote his letter resigning from the U.S. Army in April 1841 from the family mansion.
The following link from the National Park Service web site provides some interesting notes about the bridge.
http://www.nps.gov/history/nr/travel/wash/dc69.htm
After crossing the river, we could get nice views of the bridge from the side, above the roadway below that runs between the river and the Lincoln Memorial. So, it was a very enjoyable, and not at all scary walk. On the scary rating, a 2 for height, 2 for width, and 2 for length. That adds up to 6, the lowest rating yet given. I guess they can't all be scary.
Key Bridge, Washington, DC (south walkway)
Yesterday was a lazy late June day in Washington, D.C, about 90 degrees and only moderately humid. For Washington in late June, that made it a perfect day for a bridge trek.
Key Bridge crosses the Potomac River and connects Arlington, Virginia, with Georgetown in Washington, D.C. It was named after Francis Scott Key, who lived in Georgetown for a time and wrote what would become the lyrics to the Star Spangled Banner after watching (while held on a British ship) the British naval bombardment of Fort McHenry in Baltimore Harbor during the War of 1812--yes in the morning, looking at the fort, he did see that the "star-spangled banner yet wave." The Potomac River bridge bearing his name was completed in 1923, making it the oldest of a series of bridges that cross the Potomac in the Washington, D.C. area. It's a short bridge, about one-third of a mile long, with 5 lanes of traffic in all. It has sidewalks on both sides for pedestrians and bikers, with barricades to separate the sidewalk users from cars, and neck-high metal railings to separate the sidewalk users from the river below. The bridge is very popular with both pedestrians (especially joggers) and bikers. We walked on the south side of the bridge, nearest to the major parts of Washington. We started from the Virginia side, walked across to Georgetown, then recrossed.
For full disclosure, I've walked this bridge before. It's a quite manageable walk. The bridge is much lower and with much more modest views than the George Washington and Brooklyn Bridges in NYC, our recent bridge treks. But in Washington, where nothing other than the Washington Monument gets very high off the ground, you still can get a great view of the area off of the Key Bridge. We could easily see (though difficult to see in the photo below) the Washington Monument, the Kennedy Center for the Performing Arts, and the Watergate Hotel (scene of the burglary in 1972 that started the whole Watergate Affair, of course, that brought down President Nixon). In the other direction is a nice view of the spires of Georgetown University. 
I don't know exactly how high the bridge is above the river; I'm guessing 80 feet or so. Aren't there maps that boaters must have in order to know the clearance for various structures, depending on the tides and river flow? Well, I'm not a boater, and if the internet doesn't provide reliable estimates, I can estimate the height myself. 
So, walking Key Bridge is a great way to get a different perspective on Washington. And it provides a great way to get up close to the edge of a bridge. Those neck-high metal railings are solid and there is no way to fall over them, although they do shake a bit when you actually hold onto them (what a complainer). Overall scariness rating is a 10, with a 3.5 for height, 1.5 for length, and 5 for width (yes, fractions are allowed).
George Washington Bridge, lower deck
The George Washington Bridge is one of the busiest suspension bridges in the world, connecting Fort Lee, New Jersey with Upper Manhattan in New York City. The bridge is about a mile long and has 2 decks, an upper one completed in 1931 and a lower one added in 1962. Once a year they close the lower deck for a few hours early on a Sunday morning for a walk/run/bike across, starting from the NJ side, as part of a fundraising effort for the American Cancer Society. A perfect opportunity to support the effort and, yes, try out a bridge walk.
I, my wife, and reportedly another 700 or so people participated yesterday in the walk part. We may not have looked, in general, in as good physical condition as the bikers and runners (who started and finished earlier), but we were a quite determined group nonetheless. We walked right by the toll booths and onto the road for cars that went down through a short tunnel that exited right onto the lower level of the bridge. The top level was just above us, enclosing the lower level a lot and making it less bridge-like. I could hear the cars rolling over on the top level, just above us. In fact, when I stopped, I could feel the bridge moving some as it seemed to adjust to bumps from the cars overhead. A little disconcerting, and definite incentive to keep moving.
Walking on the lower deck roadway of the George Washington Bridge, with 3 lanes for traffic in our direction, meant you didn't have to get all that close to the edge. That was fortunate because the barriers on the side were rather low and somewhat open, and we were quite high off the ground from the get go. The roadway height above the water is officially listed at 212 feet, but that's from the upper level. So, subtracting, say, 20 feet for being on the lower level, puts the height at maybe 190 feet or so, and no time for acclimating whatsoever. The views were actually quite spectacular, with a sweeping view of downtown NYC. The views were obstructed somewhat by the upper deck, but were so spectacular nonetheless that I don't think I've held my wife's hand for so long since maybe our 5th year of marriage. (Unlike the Brooklyn Bridge walk, some of my fellow walkers might have guessed the reason this time, like the family that, from my perspective, went around me to ask my wife to take their picture). The spectacular views did not include the beautiful, signature bridge towers. I could see them from land.
So we pushed on. The course didn't actually allow participants to enter New York City and exit the bridge, but rather the course went to one end and then just reversed, retracing the steps on the same part of the bridge. This was an untimed, non-competitive race (though we did get numbered bibs), and so we were allowed to just go halfway over the bridge and turn right around in order to keep the distance manageable. Thus, we made it to the goal of halfway over the bridge, at just about the sign announcing the New York line, and turned around. It now officially counts as a full bridge walk if you do the same half of the bridge twice in the same walk. 
For scariness rating (height/length/width, like the old volume formula), I have to give the lower level Geo Washington an 8 for height, 5 for length, and 5 for width (nearness to solid side supports), for a total score of 18.
It's time for some shorter bridge treks, closer to home, to focus on some less high Washington DC bridges and actually get up to the edge.
Brooklyn Bridge
Under the theory that if you can walk panic-free over a bridge, then you can drive over it comfortably as well, I have started a progressive program of walking over scary bridges. The more people I speak with about my big discomfort about driving over major bridges, the more I find others who are also uncomfortable, but, unlike me, most of them will at least do it. (Of course, maybe they're just trying to make me feel better and say they're uncomfortable.) Anyway, it's time to put my walking theory to the test. Although I've done some preliminaries on Washington, DC bridges, where I live, there's nothing like New York City for lots of high, long bridge choices, and the first step in the program is a trek to the Brooklyn Bridge.
Last Sunday, May 23, was a cloudy day, but at 70 degrees pretty much perfect for a good bridge walk. With me were family who live right on the Manhattan side of the bridge, perfect guides, and my wife. The Brooklyn Bridge, if you haven't seen it, is a beautiful structure built in the 1870s and early 1880s, with the towers (for the suspension cables) built of stone. The bridge, of course, goes between Manhattan and Brooklyn. Solid as a rock. John and Washington Roebling knew what they were doing when they designed and built that bridge. But it is rather high. Fortunately the pedestrian path goes above the road, right in the center of the bridge, so while walking over it I was far from the bridge edge; no way a rogue gust of wind could do any damage, except maybe to my hat. And I guess if you fell, it would be 15 feet or so into traffic, and there were lots of cabs down there who could pick you up. And there were lots of people, lots and lots of people to keep you company. And benches to rest on. That bridge was built for walking. (Well, it actually was built before automobiles, so maybe it was built for horses, too.)
Back to the bridge walk. The bridge was about a mile long including all the approaches, and walking over it was moderately anxiety inducing, at least at first. You have to climb upgrade somewhat, and that doesn't help. And it does get pretty high up, I'll say again. But with my cool, young niece there to point out the sights and provide real perspective, and my wife to hold hands with at one point (an affectionate couple, everybody figures), and other family encouragement, it was quite manageable. A challenge, but not overwhelming so, thus a perfect start to the bridge walking experience.
The scariness of bridges can be rated, I believe, by three factors: height, length, and width (think of the mathematical formula for volume). With each of the factors getting a score of up to 10 (with higher numbers being worse), I give the Brooklyn Bridge a scary score of 13: 6 for height (135 feet in the air according to wiki), 5 for length, and 2 for width (nearness to edge, openness of bridge, solidity of side supports). No intangibles to add to or subtract from that score. 13 out of 30 leaves lots of room for bigger challenges.
Next stop may be the George Washington Bridge in a couple of weeks. We'll see.