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Transportation and Mobility

Lower Speed Limits Could Be Coming To LA (Eventually). Here's What Will Change

A speed feedback sign shows a driver was going 57 miles per hour on a street with a speed limit of 35 miles per hour.
Cities will now have more control to lower speed limits and reduce traffic violence.
(Courtesy LAPD South Traffic Division via Twitter)
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As local cities struggle to reverse the trend of growing traffic violence, compelling drivers to slow down is a key goal. One way to do that is to lower speed limits, which some cities in other states have done in recent years with promising early results.

But in Los Angeles and other California cities, speed limits are routinely raised — thanks to a decades-old method used by traffic engineers.

That’s going to change. Last week, Gov. Gavin Newsom signed Assembly Bill 43, which gives cities more control to set and lower speed limits.

Speed limits are currently set through road surveys conducted every seven to 10 years. Traffic engineers rely on a method known as the 85th percentile rule to calculate if a speed limit should change.

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A 25 mile-per-hour speed limit sign and Neighborhood Watch sign posted in Lakewood.
(Chava Sanchez

But many national safety experts and advocates say that method is dangerous and outdated, and has no place in urban settings. The rule was enacted to protect drivers from arbitrary speed traps, mostly on rural roads. But on our modern-day urban roads, people are also walking and rolling. As speed limits have ratcheted up in recent years, so have the number of pedestrians killed by drivers.

Here’s a quick summary of how the 85th percentile rule works:

During a traffic survey, engineers measure vehicle speeds along a specific roadway. The rule dictates that the speed limit should be whatever speed 85% of drivers are traveling at or below. That average speed is then rounded to the nearest interval of five.

Put another way: the speed limit is determined as roughly whatever speed 15% of drivers exceed, meaning people who drive too fast — even if they are the minority — set the pace. So, if a posted speed limit is 35 mph but a traffic survey shows that 15% of drivers are going 42 mph or faster, the new speed limit for that road would be 40 mph.

In Los Angeles and many other California cities, the rule has led to speed limits increasing over time, leading drivers to go even faster, leading to higher average speeds in the next traffic survey, leading to increased speed limits ... you get the idea.

Speed is one of the biggest factors in traffic crashes. The higher a driver’s speed, the lower the chance a pedestrian struck by that driver will survive. Add distracted driving to the mix and it’s not hard to understand why traffic deaths are surging in the U.S.

In Los Angeles, 640 pedestrians were killed by drivers from 2016-2020.

Here’s a rundown of what AB 43 will allow cities to do:

  • Local governments can lower speed limits by 5 mph below a traffic engineer's recommendation on streets identified as “safety corridors,” or near places where pedestrians and bicyclists congregate, which can include “vulnerable groups such as children, seniors, persons with disability, and the unhoused.”
  • Speed limits can stay the same or revert to a previous, lower speed on streets where safety upgrades have not been added as part of a previous traffic survey.
  • Cities can set a standard speed limit of 20-25 mph in business activity districts.
  • Law enforcement can use radar guns to enforce speed limits in senior zones (areas near designated senior facilities) or business activity districts without the justification of a traffic survey.
  • The period of time that an engineering and traffic survey justifies a speed can be extended from seven to 14 years if a traffic engineer evaluates that section of the street and determines that no significant changes in roadway or traffic conditions have occurred.
  • Local authorities can expand which streets are eligible for school zone speed limits.
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Assemblymember Laura Friedman (D-Glendale) authored the bill, which was built on years of work to rethink safety planning.

“Motor vehicle crashes are the fourth leading cause of premature death in Los Angeles County,” Friedman said in a statement. “With AB 43, communities will finally have the power to lower speed limits on dangerous roadways and make them safer for all users.”

According to the bill, “safety corridors” are roadways “that have the highest number of serious injuries and fatalities based on collision data.”

The bill also states: “A local authority shall not deem more than one-fifth of their streets as safety corridors.” Right now, L.A. has designated roughly 6% of its streets as “high-injury.” That fraction of roadways account for 70% of deaths and severe injuries for people walking.

And speed limits will not change overnight — or even in the next couple years. The new rules take effect Jan. 1, 2022, but cities might have to wait until mid-2024 to enact and enforce new speed limits. That’s because of an amendment made to the bill this summer, which states:

A local authority may not lower a speed limit as authorized by this section until June 30, 2024, or until the Judicial Council has developed an online tool for adjudicating infraction violations statewide… whichever is sooner.

That amendment was created due to concerns about equity in speeding citations. Lawmakers want to make sure low-income Californians don’t face undue financial burdens for speeding tickets, so the state is creating an online portal so drivers can look up an infraction and request a payment extension, fee reduction, payment plan, or community service in place of a fine.

The bill also calls for warning citations for drivers caught traveling 10 mph or under a lowered speed limit for the first 30 days that new limit takes effect.

You can learn more about the push to lower speed limits and curb traffic violence in the stories below.

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