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Columbia Missourian

ANY QUESTIONS: An answer about regulations on the width of roads, parking spaces

By Gregory Cornfield
May 1, 2013 | 5:11 p.m. CDT

This is part of a Missourian project called Any Questions. Submit your own question using the form below.

"Why are the roads so narrow in certain areas and also the parking lots are so tiny sometimes I can't even park in them?" — Submitted anonymously


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Thanks for the submission. According to the MoDOT engineering policy guide, Article 231.3 Lane Width, lane width regulations are taken seriously because of their effects on safety and driver comfort. 

There isn't a strict minimum or maximum, but the general lane width is about 12 feet in Missouri because it "provides desirable clearance." However, there are different widths for different types of areas.

Speed and volume of traffic are the factors that determine street width, according to MoDOT engineering policy administrator Joe Jones. For example, there are narrower lanes in urban areas with pedestrian crossings. In those cases and in rural areas with low traffic volumes, 10- or 11-foot lanes are common. On the highway where there is merging traffic or where there are continuous two-way left-turn lanes, roads can be as wide as 16 feet.

According to Shane Creech, Columbia's building and site development manager, all required parking spaces must comply with minimum dimensions that have to do with the angles of the parking space, from zero to 90 degrees.

For 90-degree parking spots, such as those at the Stankowski Field parking lot, the spaces have to be at least 8.5 feet wide and 18 feet deep.

When the spaces are at a 45-degree angle, such as in many parking garages around downtown Columbia or at Walmart, they must be 8.5 wide and 18.8 feet deep. 

There are requirements on the access aisle widths, or the room to drive between rows in parking lots, as well. Those dimensions are also correlated by the the parking angles. For 90-degree spots, the aisle must be 24-feet wide. For 45-degree parking spaces, the access aisle must be 13-feet wide.

Requirements vary, but those are the two most common types of spaces, Creech said.

Bigger might not be better

A 2002 study of crash data from all 50 U.S. states over 14 years shows states that have roads with lane widths of 9 feet or less had fewer traffic injuries. Lane widths of 10 feet or 11 feet also had fewer injuries and fatalities than 12-foot lanes. For residential streets, the same pattern was found.

"While it is not clear from these results whether there is some optimal 'safest' lane width, there does seem to be evidence that lane widths of over 11 feet do not contribute to a safer road environment," the study reads.

Additional information

According to Missouri Traffic Regulations, you can't drive on the highway in Missouri if your car or truck is more than 102 inches wide. You also can't drive on the highway if your car or truck is taller than 13.5 feet or longer than 45 feet.


To put these regulations into perspective, here is a list of some of the widest, narrowest, tallest and shortest cars from past and present. (Twelve feet is 144 inches.)

Widest cars

Widest pickup truck

Widest SUV

Widest van

Narrowest car

Tallest car

Tallest pickup

Tallest SUV

Tallest van

Shortest car

To submit your own question, fill out the form below. Supervising editor is Joy Mayer.