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Road design, stroads and road diets

Wide, straight lanes invite speed. Fewer or narrower lanes can make a road calmer and safer without new laws.

This page is a draft. Every fact links to its source, so you can check it yourself.

Most drivers pick a speed that feels right for the road in front of them. If the road looks like a highway, many will drive like it is one, even with a 35 mph sign.

What is a stroad?

"Stroad" is a nickname for a road that tries to be a street and a road at the same time. A road is built to move cars fast between places. A street is a place where people live, shop and walk. A stroad mixes both: four or more fast lanes, plus driveways, bus stops, shops and crosswalks. That mix is where many serious crashes happen.

Lane width and speed

A 2025 study of 320 city arterial roads in Utah found that each extra foot of lane width went with about 1 mph higher speeds. It also went with 38% higher odds of an injury crash on that stretch. The authors suggest 10 or 11 foot lanes in busy urban areas. (Azin, Ewing and others, Sustainability, 2025)

Research on lane width is mixed, and this is one study from one state. But the direction matches what many people feel on wide roads.

Road diets (4 lanes to 3)

A road diet turns a four-lane road with no center median into:

• one travel lane each way,
• a center turn lane, and
• leftover space for bike lanes, wider sidewalks, refuge islands or parking.

FHWA counts road diets as a Proven Safety Countermeasure. Converting four lanes to three cuts total crashes by 19% to 47%. (FHWA)

Why it works:

• Left-turning drivers wait in the center lane, so fewer rear-end crashes.
• People crossing face fewer lanes.
• One lane each way means the fastest driver no longer sets the pace.

FHWA says road diets usually fit roads that carry 25,000 cars a day or fewer, now and in the future. (FHWA) Ask the agency for its traffic counts.

A road diet can often be done when the road is repaved, by repainting the lines. FHWA notes it "can be accomplished at no additional cost" when planned with a simple overlay. (FHWA)

California's complete streets law

Every California city and county must plan for streets that work for everyone, including people walking, biking and taking transit, when it does a major update of the transportation part of its general plan. Updates made on or after January 1, 2025 must also include the federal Safe System Approach, which aims to end deaths and serious injuries. (Government Code 65302)

For state highways, SB 960 (2024) requires Caltrans to set targets for adding sidewalks, bike facilities and transit priority when it repairs highways. (California Legislature, SB 960)

What to ask for

• "When [road] is repaved, please restripe it as a road diet with bike lanes."
• "Please share the daily traffic count for [road] so we can see if a road diet fits."
• "Please narrow the travel lanes on [road] to 10 or 11 feet and use the space for bikes and walkers."

Last checked 2026-11-02.

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