Safety, Traffic, and You: The Case for Road Diets

January 5, 2011 by LADOT Bike Blog

Source: LADOT Bike Blog

Much Ado About 1 Lane

As we here at the LADOT Bike Program experienced late last year, there can be quite a kerfuffle over removing even the slightest amount of roadway space for drivers.  The controversy over the Wilbur Avenue road diet last year caused quite a bit of hand-wringing and gnashing of teeth.  In the LA Times, on Streetsblog (a few times), the Beckford Ave School PTA, the LAistLACBCCity WatchBiking in LA; coverage on the project was as broad in scope as it was diverse in opinion.

A successful road diet on San Pedro in South LA

A successful road diet on San Pedro in South LA

What it all came down to was a change of 4 lanes of traffic on Wilbur Avenue to 3 lanes  – with bike lanes added to both sides of the street.  At the time, some painted the road diet as a real estate grab for bicyclists at the expense of drivers.  There were claims that the road diet would make traffic unlivable; that it would force cars onto other streets and make the surrounding neighborhoods less safe.

Fighting for Road Diets

While some of these claims might be chalked up to the dreaded Fear of Change, it would not be productive to treat them as such.  Instead, it demonstrates a need for those who support traffic calming and livable streets to communicate their vision more effectively.  When it comes down to it, both those who support and those who oppose road diets want good neighborhoods, they want less pollution, and they want safe streets.  As roadways with excess capacity have been the modus operandi of traffic engineering for the last 50 years, it falls on the shoulders of those who support road diets to make their case.  Many have already done so.

This is our case, made in favor of Road Diets.

Road Diet – Defined

A “road diet” is typically comprised of converting a 2-way, 4 lane street into a 3 lane street with bike lanes on either side.  One travel lane goes in each direction while the center lane is marked as a “two-way left turn lane” (TWLTL).  Road diets are often planned to coincide with a scheduled repaving of a street, and thus come at little cost to the City because the road being repaved would need to be re-striped anyhow.

Lawyers Road Diet

Wilbur Avenue, Revisited

We should point out that, in the case of Wilbur Avenue, the road diet preceded the bike lanes.  Though bike lanes on Wilbur Avenue are on the 1996 bike plan, the idea of a road diet on Wilbur Avenue sprung from non-bicycle factors.  LADOT traffic engineers, after reviewing both the average speeds on the street and the history of crashes along the road, determined that a road diet would make the street far safer for all users without significantly impacting congestion.  The resulting road diet ended up providing benefits to all users.

Myths Dispelled

There are a lot of myths surrounding road diets, and they are quite pesky to dispel. That’s because, quite honestly, they appear common-sense on their face.  Take away a lane of travel?  You’re creating more traffic, more pollution, and making the road less safe.  Add a bike lane too?  You’re putting the needs of bicyclists over those of drivers.  Roadways, it seems, are a zero-sum game: If you give something to one group, you must take from another.

But if we delve into the issue a bit, it’s shown that road diets can actually be beneficial to drivers, beneficial to bicyclists, beneficial to pedestrians, and beneficial to communities. Imagine that!

Road Diets Can Improve Traffic

Seems a little strange, doesn’t it?  When a 4 lane road is below a certain volume of traffic (usually 18,000-20,000 Average Daily Trips – ADT), implementing a road diet can actually make traffic flow more smoothly.  Especially on streets that have cars making frequent left turns (like, say, a residential street with plenty of driveways), creating a two-way left turn lane creates a space for turning vehicles that won’t impact moving traffic.  Think about it another way: when a left-turning car comes to a stop in 2 lanes of travel, that direction immediately becomes 1 lane of travel.  Even worse, cars merging right will snarl traffic even further.  A road diet gives that driver a place to turn that won’t impact the free flow of traffic.

On top of that, every person who is encouraged by the bike lanes installed to ride their bike (instead of drive) on local trips around their community means one less car on the road to create congestion.

Road Diets Improve Safety – For Everyone

Road Diets improve roadway safety for all users, but let’s go through each to really drive the point home.

Driver Safety

Road Diets help improve car safety in many ways.  A study conducted by the Highway Safety Information System for the Federal Highway Administration found that road diets reduced crash frequency by 29% per mile from reconfiguration alone.   The slimmed-down roads encourage slower driving speeds, which automatically make driving safer.  They also help to prevent three specific types of car-on-car accidents.

  • Rear-End Accidents – The two-way left turn lane moves turning cars out of traffic.  In a 4 lane, high-speed road, it can be very easy to hit a car from behind when they put on their left-turn blinker and slam on their brakes.  With a road diet, the turning car merges into its own lane and out of the lane with through traffic.RD7
  • Side-swipe Accidents – The other bad outcome of a left-turning car without its own lane, a side-swipe happens when a driver swerves into the right lane to avoid someone stopped in the left lane only to hit a car traveling in the right lane.  With a road diet, both cars are already in the right lane.RD8
  • Blind-side Left Turn – A blind-side left turn is when two cars, going in either direction, both want to turn left.  The stopped car in the left lane can block the view of a car in the right lane farther back.  The car in the other direction makes the left turn only to be struck on the side by the oncoming car in the right lane.  With a road diet, both left-turning cars are in the same lane, facing each other, which removes obstructed views of oncoming traffic.RD9

Bicycle Safety

By adding bike lanes to a street with a road diet, bicycling becomes safer in two ways.  (1) Creating a space on the roadway dedicated to bicyclists, drivers will be more cognizant of bicyclists on the roadway.  (2) Creating a bike lane also has the effect of encouraging more people to get their bikes on the road.  There is safety in numbers, and the more experience drivers have sharing the road with bicyclists, the safer both bicyclists and drivers will be.

Pedestrian Safety

Pedestrians on the sidewalk will also benefit greatly from a road diet.  Not only will cars be traveling at slower speeds on the road, the addition of a bike lane creates 5 more feet of space between pedestrians and moving cars.  Drivers traveling at fast speeds are often subject to “tunnel vision”, meaning that they only register those things straight ahead and in the distance.  By bringing speeds down to a safer level, the field of vision a driver recognizes expands dramatically, making it more likely they will notice a pedestrian crossing the street before it is too late.

Road diets also make streets more enjoyable for the people who live along them, lowering street noise, discouraging speeding, and making their yards safer.  Many streets receiving road diets are residential.  By improving safety and lowering speed and noise from traffic, road diets can help to make these streets livable and enjoyable.  Yards become safer to play in and property values go up as noise and speeding go down.

Road Diets Bring Streets to Their Appropriate Scale

When complaints surface that a road diet will create “gridlock” on a street, this often refers to rush-hour periods when streets experience heavy traffic.  But what about the other 22 hours of the day when there are barely any cars on the road?  An empty 4 lane roadway is practically an invitation for a driver to speed, creating dangerous conditions for the people who live along the road in question.  A City shouldn’t have to sacrifice quality of life and piece of mind for 22 hours a day just to accommodate the other 2 hours when a street may need extra capacity.  This unused roadway requires maintenance and eats up land that could be put to other uses in a City where space is at a premium.

Road Diets Comply with State Law

The concept of road diets also satisfies AB 1358, the Complete Streets Act, which stipulates that transportation plans must comply with the needs of all users, be they drivers, bicyclists, pedestrians, or others.

What’s the Point of a Road, Anyhow?

No, really: what’s the point of a road?  Is it just to move cars?  What about pedestrians?  What about bicyclists?  What about the people who live along the street, do their needs count too?  Should a roadway being safe matter?  How safe is “safe”?

When the idea a road diet comes up, usually only the first question about the cars dominates the discourse.  But all of these other questions should figure into our train of thought when considering our roads.