Why I Support Road Diets (When They Make Sense)

Sam Morrissey explains why he largely supports the concept of "road diets" provided they are implemented in areas where they will have the desired effect.

“We’re gonna ride it till, We just can’t ride it no more.” –  Randy Newman

Last month I saw an article regarding a local Los Angeles City councilmember’s opposition to a “road diet”. This came to my attention a few minutes after reading an article posted on Fox & Hounds, where the author provided some less-than-favorable opinions on “road diets” and the overall policies and practices of California public officials and public sector employees when it comes to addressing traffic congestion.

I’ve written before that traffic in California, at least in the urbanized areas, is a reality that isn’t going away. Traffic congestion is a direct result of the state's massive population and is compounded by a discrepancy between where people choose to live and where they work (further exacerbated by housing costs and all the factors that go into choosing where one lives: schools, public services, access to public transportation, etc.).

To put it bluntly – we simply cannot think that we can just build more lanes to accommodate growing traffic.

As much as people like to talk about “induced demand”, I’d rather stick to the simple back-of-the-envelope calculation that proves we would need two to three times more lane miles of roads just to move around during congested periods a bit faster. And that won’t happen unless we want to wipe out vast swaths of homes and businesses, which would feed right back into the vicious cycle of what created this massive traffic congestion in the first place.

No, the solution for traffic congestion is simple: there isn’t one.

What we can do, however, is try to provide more options for people to get around, so that we can maximize the total efficiency of the system. Right now we allocate the majority of roadway space to vehicles, and an average personal vehicle takes up more than 100 sq ft of space. And in that 100 sq ft of space typically there is one person taking up maybe a 10 sq ft space. So that’s like a 10% efficiency in terms of the use of space, meaning 90% of the space is completely wasted.

So that is why I tend to support concepts like “road diets” when they are applied in places that make sense. In short, a road diet removes one or more vehicle travel lanes on a road segment to make space for either dedicated left-turn lanes, continuous two-way left-turn lanes, and/or bicycle lanes; sometimes all three.

From my perspective as a transportation engineer, there are factors that make road diets make sense to me, and they are:

• Lack of dedicated left-turn lanes combined with high left-turn demand
  There are a lot of streets in the greater LA area that have two lanes in each direction, without dedicated left-turn lanes. At intersections where people want to make left turns, this configuration means the left-turning vehicle can block the through movement of an entire lane. And on busy streets where the left-turning vehicle needs to wait a long time to safely execute the turn, this can cause delay and frustration for the vehicles stuck behind the left turner(s).
  
• Lots of driveways along a street segment
  Similar to the factor above, when there are many driveways along a segment, a road diet can provide a continuous left-turn lane down the middle of the road, providing both a place for vehicles entering the driveways to safely get out of the traffic stream and a place for vehicles exiting driveways to take safe refuge before entering the traffic stream.
  
• Bicycle demand
  If the street is a preferred bike route, or there are already a lot of bicycles using the road, a road diet can open up space to provide dedicated bicycle lanes, with safe buffers to protect the bicyclists from both opening car doors and the stream of vehicle traffic.
  

Back to the article about the LA councilmember’s opposition to a road diet. In this case the road diet was proposed on Sixth Street between La Brea Avenue and Fairfax Avenue. This is a predominantly residential stretch of road, running through one of the oldest multi-family developments in LA: Park La Brea. It also runs just north of the La Brea Tar Pits and the Los Angeles County Museum of Art. In most of the road segment, there are two lanes of travel in each direction, parallel parking along each side of curb and zero dedicated left-turn lanes at intersections. There aren’t a lot of driveways along this segment as most of the residences take access from side roads.

A big thing about Sixth Street is that it runs just north of Wilshire Boulevard and many auto commuters, myself included, use it as an alternate route to avoid the heavier traffic on Wilshire. I’ve seen myself – frustrated commuters using Sixth Street do frequently travel at higher speeds along the road, simply trying to get somewhere faster. This is part of the bad driver behavior I’ve written about in the past and is endemic to driving in LA and beyond. One of the neighborhood group leaders who talked about this issue was quoted in the article as saying: “Much of the traffic and the aggressive and dangerous slam-the-gas, slam-the-brakes driving that we currently have on Sixth Street is because of the lack of a center-left-turn-lane.” I’m not sure if I agree with that statement 100% as I firmly believe the aggressive driving behavior is caused by many more factors – not least of which is a severe lack of enforcement of basic traffic safety laws.

Other neighborhood groups were quoted in the article as opposing the road diet, noting that it could result in more cars shifting from Sixth Street to other east-west streets, meaning the aggressive and unsafe driving behaviors would simply move from one street to another.

The people supporting the road diet point to safety improvements as the reason for the proposal. Safety is crucial and should be the motivating force in transportation improvements. Some of the supporters were quoted in the article as saying “Removing traffic lanes would help slow down traffic, making the street safer.” I just can’t fully support that last statement. If lanes are removed without thoroughly assessing the issues, without addressing the primary factors that make road diets a sensible solution, they actually run the risk of frustrating more drivers, which could cause drivers to behave in even worse ways. I’m in no way throwing out the argument that a road diet creates unsafe conditions. Rather, I’m saying that improperly implemented traffic solutions can frustrate an already frustrated, aggressive and unsafe driving populace.

In his opposition to the road diet, the article noted that the councilmember’s “‘office will be moving forward with’ adding left-turn pockets at the intersection of Sixth Street and Hauser Boulevard, a peak-hour left-turn restriction at Burnside Avenue, and several crosswalks”. This seems like a smart move in terms of policy because from my perspective Sixth Street doesn’t meet the factors noted above. Specifically:

• Lack of dedicated left-turn lanes combined with high left-turn demand
  Although there are no dedicated left-turn lanes on Sixth Street, my personal experience is that most drivers understand this potential and change lanes when a vehicle ahead of them starts to signal for a left turn at an upcoming intersection (well, when some people do). It doesn’t seem to cause massive delays for through vehicles, which is probably why Sixth Street is a preferred alternative to Wilshire. And that is why the councilmember’s proposal to add a left-turn pocket at a specific intersection makes sense. I’d prefer to see an evaluation of all intersections and only if a majority of intersections required a dedicated left-turn lane would the road diet make sense.
  

• Lots of driveways along a street segment
  This condition doesn’t exist on Sixth Street, so there really is no benefit of adding a center-turn lane. And what that would do, effectively, is remove a lane. So even though a travel lane might only be 10% efficient, this new center lane would have a nearly 0% efficiency – not a great use of limited space.
  
• Bicycle demand
  This is a tough one. In the city of LA, bicycle advocates pushed to be allowed to use the Wilshire bus-only lanes. I wouldn’t ride on Wilshire personally because of the high vehicle speeds and erratic behavior. I’ve never seen a lot of bicycle traffic on Sixth Street and can’t say there’d be more if a dedicated bike lane was added. From the standpoint of justifying a road diet, however, I just don’t see the math working out.
  
  

The Bottom Line

I personally believe that the councilmember is making the right move from both a policy and roadway safety perspective. On the stretch of Sixth Street in question, the factors just don’t currently present themselves to fully justify a road diet. Now, on the flip side of this discussion, I would like to see the councilmember come out in support of more beneficial safety improvements – including automated red-light photo enforcement and automated speed enforcement. Combined with the improvements his office suggests, these could make some real positive impacts on safety on Sixth Street and throughout Los Angeles.

About the Author

Sam Morrissey previously served as an associate vice president at Iteris, leading its Mobility Services group.