by Dom Nozzi
I’ve spent the past several years, as a city planner, learning what works and what doesn’t work with regard to transportation planning. I’ve done research, and talked with a great number of city residents and transportation experts. I even wrote a book (and a second, shortly).
In many ways, what I have learned is the opposite of what I, and most other people I know, have always believed. The overwhelming consensus is that the way we’ve done things for the past few decades no longer makes sense.
What I have learned leads me to strongly recommend that cities put a number of their town center streets – particularly their Main Street – on a “road diet,” where travel lanes are removed and the road becomes, say, 3 lanes rather than 4.
Again, making a road more modest is the opposite of what we’ve always believed. But there are a number of very important reasons why a road diet (such as a conversion from 4 lanes to 3) would be beneficial for a city:
No Meaningful Loss of Capacity. At first glance, it would seem irrefutable that removing travel lanes from a street would create congestion. However, the inside lane of a 4-lane street is generally used as a left-turn lane and therefore cannot be used as a through lane. As such, only the curb lane can handle most through trips if the street has no left-turn lane. Consequently, a 3-lane street with a left-turn lane handles about the same number of vehicles as a 4-lane. In fact, studies show that 4-lane and 3-lane streets carry about the same number of vehicles.
No Spillover. Because there is no real loss of capacity, going from a 4-lane to a 3-lane street would not cause any increase in “spillover” vehicle trips-the trips that might be diverted to adjacent streets near the road-dieted street by motorists seeking to avoid a congested street.
More Safety. A 3-lane is noticeably more safe than a 4-lane, resulting in a substantial reduction in crashes. Vehicle speeds go down, there is less variability in vehicle speeds, and there is less speeding. In addition, there is a big reduction in what engineers call “conflict” points and an increase in “sight distance” for turning and crossing traffic on a 3-lane. This is particularly important for many of our senior citizens who drive, since fewer conflict points and increased sight distance means fewer decisions and judgements have to be made to enter or cross a 3-lane street. Similarly, a 3-lane reduces the street-crossing distance where a pedestrian must be exposed to moving vehicle traffic, and creates a “refuge area” where a pedestrian can safely wait until there is a gap in traffic and safe crossing is possible (4-lane streets do not have a refuge area). A 4-lane street is a hostile, unsafe, high-speed highway that creates a safety barrier for those trying to cross it. For these reasons, a 3-lane street would be substantially more “permeable” for residents seeking to cross the street.
No Loss of Travel Time. Even though average vehicle speeds are lower on a 3-lane, travel time either stays the same or actually declines, according to studies I have seen.
Reduction in Blight and Strip Commercial. One of the regrettable aspects of a great many 4-lane streets is that the high-speed nature of them often incrementally converts the street into an ugly, glaring, blighted, “Anywhere USA” commercial strip featuring huge seas of asphalt parking and buildings that retreat from the hostile the street. A 3-lane street can lead us back to an attractive, walkable, human-scaled street and building design that can restore a civic pride in the street, instead of being a street we don’t care for. Streets that are treated by removing travel lanes becomes a drive-to destination, rather than a drive-through “no man’s land.”
Improved Health of Main Street Land Uses. One thing that nearly all road diets deliver as a community benefit is the restoration of a healthy place for buildings. The “diet” will result in improved retail and office health along the dieted street, and actually make it possible again to see the establishment of new residences along the street. Indeed, dieted streets can become what we have traditionally called a “shopping street.” A bustling, fun, safe street that induces community pride.
It is a no-brainer. Put your “overweight” town center streets on a road diet.
speeding, inattentive driving, road rage, traffic infractions and motorist impatience. Former “shopping streets” (often including residences) become drive-throughs instead of drive-tos. Life for the now declining number of pedestrians, bicyclists and transit users becomes unsafe, inconvenient and unpleasant. Likewise, the street loses residences and businesses due to the more hostile conditions. The one-ways also require a great deal of extra motorist travel distance due to backtracking.
use rate), and the parking meter revenue must be dedicated to improving the streetscape in the vicinity of the meters, rather than being dispersed citywide. 
Dom's Plan B Blog 