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Thursday, July 30, 2009

Imagine the Beltway at New Hampshire Avenue

The Beltway is a dangerous road full of daunting lane shifts and bottlenecks that bring the ire of even the most seasoned drivers. The area around its junction with I-95 receives a lot of attention, but the problems on its northern counterpart often go ignored.

Westbound 495/95 is four lanes until the interchange with US-1. Both ramps from US-1 to The Beltway create additional westbound lanes, making it six lanes wide at the 95/495 split. Four lanes continue westbound. The ramps from Southbound 1-95 swell the roadway back to six westbound lanes. One lane splits off as an exit for northbound New Hampshire Avenue. A flyover ramp replaces it, creating a weave-style merge for cars entering the westbound Beltway from NH northbound and exiting the Beltway southbound. After the interchange, the highway quickly bottlenecks from 6 lanes back to four. Sound confusing? Try diving it.

A driver who wants to exit the Beltway at New Hampshire Avenue northbound must cross two lanes of traffic even if they were in the far right lane before the I-95 merger. For drivers wishing to head southbound on New Hampshire, they must still cross an extra lane of traffic and then contend with merging across the cars entering the Beltway.

View NH Av Interchange in a larger map

My idea would be to remove one westbound lane where northbound 1-95 splits off to the north, making the stretch between northbound I-95 and southbound I-95 three lanes. When the two southbound lanes join the Beltway, it will be five lanes wide.

Next, remove the exit to southbound New Hampshire Avenue, eliminating a dangerous merge area. Instead, direct that traffic down the northbound exit to a left turn, much like the Georgia Avenue, Connecticut Avenue, and University Boulevard exits off the westbound Beltway. The intersection at the end of the northbound exit is already signaled, it would only need provisions for left turning (southbound) vehicles.

In addition to making this interchange safer for Beltway drivers, it creates a safer environment for pedestrians on New Hampshire Avenue. Not by much, but it would be a start. But just for kicks, I threw in a small street grid, in hopes that Hillandale may one day be a little more pedestrian friendly. They already have a LEED Gold building, perhaps more positive change is on the way.

Tuesday, July 28, 2009

Circular Logic

Tonight I did a very friendly thing and helped a buddy of mine move from Columbia to Gaithersburg. It's a cumbersome route to drive, but I was determined to avoid the rush hour freeways and see what little remained of the northeastern Montgomery County rural areas on the back roads. It is not actually a bad route, if not for the constant stop-and-go through Ashton, Olney, and Gaithersburg.

Woodfield Road, which is currently being widened, at Fieldcrest Road. This intersection could have been a roundabout, but instead the county has decided to induce more demand along this route. (Photo by thisisbossi)

Most of my route (MD-108 to Fieldcrest Road/ to Woodfield Road/MD-124) was two lanes roads, but these two lane roads would mushroom to as many as seven lanes at major intersections. This phenomenon is obviously to prevent long backups at these traffic lights. And in such suburbanized areas, people are driving to get anywhere, hence the percieved need to prevent such backups.

But I noticed that, even during the end of rush hour, I would sit at a traffic light for as many as 90 seconds without a single other car at the intersection in any direction. This made me think of something I read via GreaterGreaterWashington's Dinner Links a few days back; roundabouts as a traffic solution.

As time goes by, intersections grow wider, adding capacity to these suburban intersections. the stretches between the intersections are often are widened shortly after. I noticed this happening on Woodfield Road during my drive. Once this happens, the overall capacity of the road is increased, which induces demand, ultimately contributing to more traffic.

Perhaps before we widen roads in suburban Maryland, we ought to try putting roundabouts in at these intersections. They would improve the flow of traffic without adding more capacity and inducing more demand. Overtime, this would save billions in construction costs. It would reduce the maximum speeds of the cars driving the routes, making the roads safer. But it would not add more time to the trip. During off-peak hours, it might even speed up trips. Other safety bonuses: roundabouts decrease the number of points for a collision to take place by 75%, and also eliminate people speeding up to make a green light. It would save gas, as the article in the above link mentions, accelerating from a dead stop is the least efficient thing an internal combustion engine can do. This would decrease the need for that greatly. And if Gaithersburg ever decides to return to its once-progressive planning style, it would facilitate pedestrians more safely and efficiently.

The fact of the matter is that this could serve as a solution at suburban intersections anywhere, and even many urban intersections. Once the capacity is added and the demand is induced, however, it would be a lot tougher to implement. So why haven't we started doing this on our two- and four-lane roads? Why perpetuate a cycle of increased traffic when we could more easily perpetuate a cycle of efficient traffic flow on our suburban routes?

Friday, July 3, 2009

Imagine a Better Rail Link to Frederick

I have always hated Interstate 270. Always. It is a little confusing with the local and HOV lanes. It is much, much wider than it ought to be, creating huge bottlenecks in northern Montgomery County and at the Beltway. It is preposterously ugly, unbearably congested, and I feel particularly unsafe driving it. It is, in my humble opinion, very poorly planned. The last thing we need is more of it. But that is what they want to give us.

Lots of people travel this corridor in both directions every day. Frederick County has a population of a quarter million and growing. The Bethesda-Gaithersburg-Frederick corridor has a population encroaching on five times that number, or roughly 20% of the Metropolitan area population. Downtown DC and Frederick are about 40 miles apart from each other. So this is a long corridor with a lot of people on it. A transportation solution must be found.

Obviously MARC's Brunswick Line is not getting it done. Its circuitous route through Brunswick adds several additional miles to the trip. Stops at small stations like Garrett Park, Washington Grove, Boyds, Barnesville, and Dickerson. Only 7000 people are riding this line daily (warning: pdf), and it is pushing its capacity. Even MARC's 2035 plan (pdf) only raise the capacity 26,000 per day (pdf). Meanwhile, between 75,000 and 108,000 vehicles clog I-270 every day. Imagine if we were talking about a solution that was faster than an expanded freeway or an improved MARC.

Widening I-270 is a colossal failure of an idea. Creating a bigger bottleneck at the Beltway for commuters from Frederick is just going to increase the number of cars that will sit on the parking lot that is 270 southbound in the morning. Here is my vision for a rail solution:

View Frederick Line in a larger map

If local transit (light rail, buses, etc.) ferried these commuters to a few stations, the trains could make fewer stops and travel at higher speeds. A system like this, I envision an average speed of 90 mph. Eight stops along the way, that's it. Stops at major transit centers and major suburbs along I-270.

There is nothing on the books for a direct high speed service between DC and Frederick. There are plenty of other transit priorities at this time. And I understand that some people have no choice but to drive to their jobs. I am one of them. But I live six miles from my job. If I am going to subsidize someone else's extra-long commute, I want to do it with a system that will work, not one that will only increase the number of cars that are wasting fuel while sitting idly on a congested freeway.

Thursday, July 2, 2009

Do American Highways Make the Grade?

During my recent travels to Germany, I was surprised and impressed by how much I enjoyed driving on the freeways. This past weekend, I realized exactly what it was that was so enjoyable about them. I drove a giant square from Laurel to Bethesda to Frederick and back to Laurel, on Interstates 95, 495, 270, and 70. I never thought I would say this, but our highways are under-engineered.

The A-6 in Germany above grade with an exit to an arterial road running at grade. Photo copyright David Murphy.

I drove through five different Western European countries on my recent business trip to Germany. The highways in all of them were straighter and flatter than our highways. Because of this, their footprints were much smaller, the lanes were not as wide, and their speed limits were much higher, if there was a limit at all. This placed much of the highway on bridges and in cuts, allowing for far less impact on the local road networks (which was already minimal because European freeways rarely run through cities like our interstates). The terrain of Germany, France, and the low countries is at least as hilly as Maryland's, so it was a very notable comparison between the grading of their freeways and ours.

Interstate 270 to Frederick is one of the straightest highways around DC, but after driving on the Autobahn it was very obvious that there are many more minor curves, and the road tightly hugs every elevation change along the way. The A-6 in Germany, by contrast, tended to remain flat through the dips and rises of the terrain. The sight lines were far greater; I could probably see at least a mile ahead at most points on the freeway. Speed limits were generally 100-130 km/h (62-81 mph) and most of Germany had no speed limit except around major interchanges. (Where Germany has speed limits, they are strictly enforced). Combined with laws prohibiting passing on the right and requiring slower cars to make way for faster cars coming up behind them, I saw little congestion on European highways, even during rush hour, even through construction sites.

On Sunday while driving down I-270 just south of Frederick, traffic slowed to about 20 mph for no apparent reason. Perhaps if this road had been properly graded when it was constructed, they would not be considering widening this stretch (pdf). Adding lanes will only generate more traffic (pdf) and make the bottleneck at the Beltway even bigger. Does this mean we should completely regrade I-270? Of course not. But it does mean that perhaps lack of lanes is not what is making traffic so annoying on 270.

Obviously, grading a highway this way is much more expensive. However, if it facilitates better traffic flow, in the long term it pays off. It pays off even faster when considering that the footprint of the highway will be significantly smaller. More even grading and straighter carriageways will also save fuel. Over time, this will add up to quite a bit of fuel. Perhaps it would help lower our per capita road deaths a little more. Right now the only thing decreasing our highway fatalities is the rising fuel costs. Instead, we allow new sub-par meandering freeways like the ICC wind their way through our rural landscapes without putting the structure into the infrastructure. It is no wonder traffic projections predict that the road will not alleviate traffic on any other area highways.

Am I saying we should tear up and rebuild all of our freeways in America? Absolutely not. But love them or hate them, freeways are the most important part of America's transportation infrastructure right now. Before the inevitable new highway is approved, it should be facing scrutiny over curves and small elevation changes like the ones on existing area highways. It could allow for better connectivity, more efficient land use, and it might even save fuel, money, and lives.