It dawned on me recently, as I drove around the Washington, DC area, that there seemed to be an inordinate number of reversible road lanes that switched directions on regular schedules. The occurrence that got me thinking about this was a one-block section of Washington Boulevard (map) on the western edge of Arlington’s Clarendon neighborhood
Washington Blvd., Arlington, Virginia, USA
via Google Street View, July 2014
I’ve driven through that slot a number of times and I never gave it much of a second thought. It seemed rather self-explanatory. Overhead lights with green arrows and red x’s denoted lanes that could be traversed depending on prevailing morning or evening traffic patterns. It made sense even if it lasted for such a short distance. It was the only three lane segment with four lanes radiating from either end. It saved on construction costs.
The variety of different types of reversible lanes also surprised me as I started ticking-off some nearby examples.
Stupid Young Driver on Cell Phone in Closed Lane on Chesapeake Bay Bridge! by William Johns, on Flickr
Creative Commons Attribution 2.0 Generic (CC BY 2.0)
The Chesapeake Bay Bridge (map) connecting Maryland’s eastern shore to the rest of the state provided yet another example of overhead lights signaling traffic flow. The bridge accommodated prevailing traffic to and from Atlantic Ocean resorts especially during the summertime. More lanes opened towards the beach on Fridays and pointed back towards home on Sundays, almost like the ebb and flow of tides.
Overhead lights exposed an inherit problem: people needed to understand that lanes could reverse and they also needed to know what the symbols meant. "Stupid Young Driver on Cell Phone" had obvious difficulties with one or both of those concepts.
Just a Sign
'Signs' — Chain Bridge (VA) January 2014 by Ron Cogswell, on Flickr
Creative Commons Attribution 2.0 Generic (CC BY 2.0)
Chain Bridge (map) had three lanes stretching across the Potomac River between Arlington and Washington, with the middle lane reversible. Only a single sign told motorists about the unusual situation (Street View). Presumably daily commuters traveling over the bridge during critical hours would already understand the situation. Woe to the poor visitor who happened to cross the bridge at an inopportune time and not see the sign.
A Machine Does All the Work
Roosevelt Bridge, Washington, DC, USA
via Google Street View, August 2014
Another Potomac River bridge between Arlington and Washington, the Theodore Roosevelt Bridge (map) offered a better solution. The reversible section had a concrete barrier to keep drivers from making a mistake. An odd little machine moved the barrier twice a day to accommodate commuters. This unusual arrangement was created by Lindsay Transportation Solutions.
The moveable barrier system enables the DOT to quickly reconfigure traffic lanes and directional capacity on the bridge in less than 15 minutes (the bridge is just under one mile in length). The Barrier Transfer Machine (BTM) safely transfers the barrier one or two traffic lanes at speeds from seven to ten miles per hour. A magnetic tape grooved into the pavement guides the BTM and ensures precise placement of the barrier wall.
That seemed a lot safer than signs or overhead lights.
Completely Reversible with a Sign
IMG_4012 by bankbryan, on Flickr
Creative Commons Attribution-NonCommercial-NoDerivs 2.0 Generic (CC BY-NC-ND 2.0)
Some of our local roads were completely reversible. The Rock Creek Parkway (map) — actually called the Rock Creek and Potomac Parkway in official terms, which I didn’t know until a few minutes ago — operated with two lanes in both directions most of the time. However in the morning all four lanes headed towards Washington and all four lanes returned traffic to the suburbs in the evening. Monday through Friday. Except Federal holidays. Make an error reading a sign (Street View) and find oneself heading towards the wrong way on a four-lane highway.
I would stay away from here on Columbus Day. Federal government employees are about the only people who get the day off. Imagine everyone else forgetting about that quirk and thinking it was a normal Monday commute. Yikes!
Completely Reversible and Safer
Interstate 395 – Virginia by Doug Kerr, on Flickr
Creative Commons Attribution-ShareAlike 2.0 Generic (CC BY-SA 2.0)
A stretch of Interstate 95 and Interstate 395 (map) from Northern Virginia into the District featured two High Occupancy Vehicle (HOV) lanes that switched directions for the morning and evening commutes, sandwiched between and completely separate from the regular highway lanes. These are being converted into High Occupancy/Toll (HOT) lanes although the concept will remain largely the same.
These seemed considerably safer. Barrier arms blocked access to ramps that led to these special lanes so that cars traveling in the "wrong" direction couldn’t make a mistake. The arms raised when the lanes reversed and it was safe to travel that direction again.
There were several more reversible lanes in the area that I didn’t have space to mention. Also Wikipedia had an entire article devoted to reversible lanes in other parts of the world so I imagined they were rather prevalent. It was funny how I’ve grown so used to seeing them that I never considered how weird they seemed conceptually.
I stumble across the most fascinating bits of information in unexpected places. It happened this time as I examined the unusually-wide median strip between the eastbound and westbound lanes of Interstate 8 in southern California. I learned of a nearby oddity further down the highway while reviewing various roadfan websites.
A motorist will encounter the lowest overland elevation in the entire Interstate Highway System just to the east of the extreme central reservation I’d discovered earlier. It is listed as 52 feet (16 meters) below sea level by the U.S. Government’s Federal Highway Administration.
It’s not the lowest elevation of any road of any type within the U.S. — that’s Badwater Road in Death Valley which provides access to the lowest public restroom in North America (~ -282 ft, -86 m) — just the lowest natural point of elevation in the Interstate Highway System. It’s still pretty impressive, though.
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This happens in the vicinity of Exit 107 where I-8 crosses the New River. Notice the channel. The road dips down here as it crosses the river over a short bridge. Where, I wondered, could the New River be flowing if it was already more than fifty feet below sea level here? Certainly it would not be flowing to the sea. It much be part of an endorheic basin, and indeed that is the case.
The New River begins in Baja California, Mexico where it’s known as the Río Nuevo. It passes through the wonderfully conjoined portmanteau cities of Mexicali and Calexico. From there it flows under the I-8 bridge west of El Centro, and on to the Salton Sea. The surface elevation of the Salton Sea is -226 ft (-69 m) so whatever flows along the New River won’t leave the Salton Sea on its own unless it’s able to evaporate.
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That’s a problem. This Street View image from the point of lowest Interstate elevation shows one of the most polluted bodies of water in the nation. Sewage, pesticide-laden agricultural runoff, and industrial waste from businesses located along the ditch then dump into a basin without an outflow. Toxins and pathogens collect in extreme concentrations, creating a most foul situation. Those driving at high speed along I-8, crossing this point of lowest elevation, likely never consider the drawbacks of this dubious honor.
Let’s put one more asterisk onto the claim. There are other places along the Interstate Highway Systems with a lower elevation. However, they are located in tunnels. A similar situation exists in Canada.
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The Intertubes claims that the Fort McHenry Tunnel carrying I-95 traffic through Baltimore, Maryland represents the absolutely lowest Interstate elevation at 107 ft (33 m) below sea level. It passes in close proximity to historic Fort McHenry, as implied by the name, the battlefield site inspiring the Star Spangled Banner. It then drops below Baltimore Harbor. I’d post a Street View image except that the interior of a tunnel isn’t exactly the most exciting scenery available (check for yourself if you must).
While the exalted position of the Fort McHenry tunnel seemed to be conventional wisdom for the cyberspace masses, it was not the only candidate offered. I discovered numerous other claims. I could not, however, nail-down a definitive source. Another option included the I-93 Thomas P. "Tip" O’Neill Tunnel, part of the Big Dig project in Boston, Massachusetts. The I-64 Hampton Roads Bridge-Tunnel in Virginia was also mentioned frequently. I know we have several roadfans who read 12MC regularly so hopefully someone can provide a proper citation and we can put these issues to rest. I’ve driven through all three of these tunnels so I’m covered no matter how it turns out. Funny, I never realized I was experiencing a true geo-oddity during any of my transits.
I’ve never driven on I-8 through California though. I look forward to experiencing both the wide median and the lowest overland elevation someday.
A query landed on the Twelve Mile Circle from a search engine as they often do. Our anonymous visitor was curious about "capital cities interstate." It took me a little while to figure out what he really wanted to know. I believe he was curious to discover the small number of U.S. state capital cities that are not served by Interstate Highways, a topic covered previously. That’s my guess and that’s where the search engine pointed him so hopefully all went well.
That got me thinking about the query differently. What if I took it literally? Let’s imagine a scenario where someone wished to visit state capitals on a long-distance trip. I don’t know, maybe our traveler wanted to create a photo collection of state capitol buildings or something — don’t be judgmental, people do that! — and for some reason he wanted to remain on a single Interstate Highway the whole time between points. Which Interstate Highway connects the most state capitals?
I didn’t conduct an exhaustive examination so I can’t guarantee that these are the absolute best results. I think they’re pretty good though.
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Interstate 80 seems to be the most optimal example to me. Five state capitals can be found along its length: Des Moines, IA; Lincoln, NE; Cheyenne, WY; Salt Lake City, UT; and Sacramento, CA. This can be accomplished with 27 hours of driving over 1,724 miles (2,774 kilometres). I’ll add a little caveat at this point. The highways I examined may not always plow directly through each city. Sometimes they provided a bypass in close proximity while skirting the city center. Thus, whether a highway actually serves a city depends upon one’s tolerance to proximity. The Interstate 80 example seemed to be the cleanest one with minimal bypassing based upon my quick eyeballing.
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I found another example in the crowded northeast corridor along Interstate 95. I wasn’t too surprised. States tend to be smaller with capitals located near the Atlantic coast, an artifact of colonial times when ships were a primary means of transportation. Five state capitals aligned again: Augusta, ME; Boston, MA; Providence, RI; Trenton, NJ; and Richmond, VA. Boston might be the ringer here. I-95 bypasses the city core by several miles (map). I can sense an opportunity for someone to claim that I-95 doesn’t really run through Boston. Perhaps one could also add the national capital, Washington, DC to this list. I know, it’s a slippery slope. All of these capitals could be claimed during a 747 mile (1,200 km) trek. Under the absolutely best conditions it would require 14 hours of pure driving hell. This is not a journey for the timid.
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I’m going to call Interstate 35 a four-plus example. There are definitely four state capitals: St. Paul, MN; Des Moines, IA; Oklahoma City, OK; and Austin, TX. The "plus" pertains to Topeka, KS. Topeka isn’t located on I-35, however, it’s found on a spur of that highway with the designation I-335. I might let that one slide except that it’s a fifty mile (80 km.) spur. It doesn’t have sufficient proximity, in my opinion, for me to count Topeka as being located along I-35.
There were three other Interstate Highways that I found with four capital cities along their routes.
- Interstate 20: Columbia, SC; Atlanta, GA; Montgomery, AL and Jackson, MS
- Interstate 40: Raleigh, NC; Nashville, TN; Little Rock, AR and Oklahoma City, OK
- Interstate 70: Columbus, OH; Indianapolis, IN; Topeka, KS; and Denver, CO
I-20 seems to offer a particularly good return on investment. The total driving distance would be a relatively compact 624 miles (1,000 km) along a nice route without the nail-biting traffic found in the northeast. I discovered a US Highway that also fit the bill. US Route 50 connects Annapolis, MD; Jefferson City, MO; Carson City, NV and Sacramento, CA.
Looking at pairs, which two are the closest together?
- Interstate 95: Boston, MA to Providence, RI (50 mi/80 km)
- Interstate 93: Boston, MA to Concord, NH (68 miles/110 km)
- Interstate 89: Concord, NH to Montpelier, VT (118 miles/190 km)
Another non-interstate, US Route 13, also does remarkably well with Dover, DE to Trenton, NJ (113 mi/182 km)
And the most frustrating? Denver, CO and Harrisburg, PA are both on Interstate 76. Hartford, CT and Boise, ID are both on Interstate 84. However, one cannot drive contiguously using the same highway between the pairs. The segments, despite common numbering, are separated by thousands of miles.
This was a fun albeit completely unproductive way to spend an entire evening.