Road diet: Solving traffic problems with fewer lanes

By Justin Campbell

Road Diet

Sometimes roads need to go on a diet.

This is not to say they get thinner or use fewer materials. Instead, a “road diet” maintains the same width of the road while removing vehicle travel lanes and utilizing those spaces for other uses and travel modes.

When congestion on roads increases, the usual step is to widen the road and add more lanes. Sometimes the problem is not caused by a high volume of vehicles. Congestion can also occur when there are road conflicts, such as:

  • A high number of left-turning vehicles
  • Buses making stops
  • Mixed traffic flow with bicyclists

Cities are also interested in road diets because they want to see less vehicles simply passing through, which provides no benefit for the community, wears down the pavement, and makes noise. Road diets allow communities to make a “complete street,” one that offers room for bicyclists, buses, and parking to access local businesses. They want to make a street that’s better for the people living in their community, one that’s safer and more beautiful. A road diet helps them achieve that.

What a ‘road diet’ looks like

The most common road diet is going from a four-lane road to three lanes, with two lanes of through-moving traffic and a two-way left-turn lane in the middle. The center lane can be a little wider, or be a safe refuge to help pedestrians cross the road safely.

The space of the former fourth lane can be turned into:

  • Bike lanes
  • Turn lanes
  • Wider shoulders for bus stops
  • Parking spots

When commercial or residential areas build up around travel corridors, lots of access points are added, such as driveways. Instead of through-traveling traffic, there is a shift to more turning vehicles, causing congestion. By adding a two-way left-turn lane, congestion is reduced because the impediments for through-traveling vehicles are removed.

Why go on a ‘road diet?’

Road diets are safer for traffic because they:
  • Bring bus stops to the shoulder
  • Remove bicycles from traffic
  • Make traffic move safer by keeping the speeds more constant – there are less variations caused by public transit, bikes and turning vehicles
They are also safer for pedestrians because:
  • There are less live lanes to cross
  • They can cross the road in two phases, as the middle lane can be used as a refuge
  • Bicyclists are removed from main traffic and given their own space
Some residents might worry that there’ll be more congestion when lanes are removed. Once they drive the road after changes are made, they see traffic flow increase because most of the road conflicts are removed from the main lanes. While a “road diet” might not be the first solution thought of when traffic congestion problems arise, they can be another useful option for cities that benefits both the community and drivers.

Justin Campbell, PE   As a transportation engineer, problem solving in a collaborative- and team-based environment is the key to my clients’ success. Positivity and optimism allow me to see things through the lens of possibilities and I enjoy sharing this type of energy with my clients and colleagues.

Justin Campbell, PE

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