After writing a storyabout plans for variable speed limits on partof I-465, I received a flood of emails and calls.
I can sum up the feedbackwith two sentences: Why would the state lowerthe speed limit on I-465? It's too low already!
It's no surprise so many people think the 55 mph speed limit on Indianapolis' beltway is too slow. Forget the Indianapolis Motor Speedway, the left lane of I-465 can feellike the Racing Capital of the World.
A driver going 10 mph over the speed limit in the fast lane may find themselves tailgated by faster cars or even passed on the right. Going the speed limit can be uncomfortable, even in far right lane.
That's what I learned when I recently drove a full lap of I-465 with my cruise control set on 55 mph. I didn't pass a single vehicle during the 50-plus mile loop. Merging to a middle lane to make room for vehicles coming from an on-ramp was not always easy.
I could feel gusts of air as some cars, including a hearse, blew past me. At one point semis passed me on both sides at the same time. I tried to stay as far right as I could, yet some drivers still passed me on the right, at one point even using an exit lane to do so. Wave after wave of cars big and small passed me in all lanes.
Traffic data backs up my uneasy feelings: In one count, more than nine of every 10 drivers went over the limit. Despite this, changing the speed limit is no easy task.
This month I set off to learn just how fast people actually drive on I-465 andwhy it has a 55 mph speed limit.
How fast people drive on I-465
One of the notes I received from readers about I-465 speed limits mentioned the real-time travel boards you see along interstates. The signs,often blue,use a combination of cameras and sensors to tell you how many minutes it will taketo drive a particular distance.
Those boards are evidence that traffic along area interstates is not going the speed limit.
For example, a board on southbound I-465 on Dec. 31 told drivers it would take them 10 minutes to drive 11 miles.When driving 60 mph, you drive one mile each minute. That means if the number of miles exceeds the minutes it will take to get you there, you're going faster than 60 mph. To travel 11 miles in 10 minutes, you would need to average 66 mph, which is 11 mph over the speed limit.
It's a literal sign that drivers are not going the speed limit.
I usedthe Indiana Department of Transportation traffic database to explorejust how fast drivers go.
The numbers can be astonishing. INDOT recorded vehicle speeds at one spot of I-465 on the northwest side for 13 days in December. They recorded over 1.1 million vehicles. 96.3% were going over the speed limit.
Well more than half —62.5% — of the vehicles were recorded over 65 mph, driving more than 10 mph over the limit.
A review of INDOT speed counts from nine locations around the loop between 2014 and 2020found the percentage of vehicles going over the speed limitranged from 70.2% to 96.3%.
These are not perfect numbers. Factors like weather and crashes affect speed, sometimes dramatically. Data from days with snow storms would show slower speeds, for example.
From May: People are speeding during the pandemic but tickets are down
But it's safe to say many drivers are ignoring the speed limit.
Speed is limited by law
Indiana law determines how high speed limits can go.
Because I-465 is within an urban area as defined by state law, its speed limit cannot be above 55 mph.
INDOT can lower the limit if an engineering study shows a lower speed is necessary for safety or traffic reasons.
To learn more about how speed limits are set, I spoke toYiheng Feng, an assistant professor in the Lyles School of Civil Engineering at Purdue University.
He said generally speed limits are set using physical factors, such as the number and width of lanes, whether the freeway is divided, and how far ahead drivers can see.
Using these factors, engineers build interstates with a design speed in mind. On the newer sections of mainline I-465, that design speed is 70 mph, an INDOT spokesperson said.
But he said speed limits can also be set by considering driving behavior. A common measurement for this is the 85th percentile:the speed85% of people drive at or below.
In the speed counts at the nine locations I referenced earlier, 85th percentile speeds ranged from 60 mph to 79mph — all over the speed limit.
Feng said Utah decided to raise some of its limits after seeing 85th percentile speeds well above the limit. He said the goal is to have all vehicles going about the same speed.
"Alot of studies have shown that although speeding is a factor of crashes, speed variantis a more significant contributing factor to the crashes," he said."Because if you have different speeds, the higher speed vehiclesmay cut in,which may cause a brake of the following vehicle. That can be dangerous."
He said thevehicles in line behind the cut-off vehicle often brake even harder, creating a shockwave in the highway that can create congestion even if no crash occurs.
There were 1,383 property damage crashes on I-465 last year, according to Indiana State Police.Ninecrashes were fatal, and 228 resulted in injuries.
Variable speed limits
Reducing these crashes is one goal of INDOT's proposal to use variable speed limits on the southeast side of the I-465 loop. The speed limits would drop in 5 mph increments to as low as 45 mph during times of congestion.
The idea is that lower limits would help everyone go the same speed during times of congestion, preventing the types of chain-reaction slowdowns that Feng described and making traffic clear faster.
Variable speed limits: Here's the plan for I-465 on the southeast side
Feng said how effective variable speed limits are depends on how many people follow it. This would be the first permanent use of variable speed limits in Indiana, but he said studies from elsewhere have shown most drivers do not follow the changing limits.
In a December meeting, project leaders said how much drivers pay attention to the changing speed limits depends on how much they're enforced.
Indiana State Police issued3,445 speeding and reckless driving citations on I-465 last year.
Sgt. John Perrine said the goal is to get people to slow down voluntarily. Sometimes troopers do this by using what he called "high-visibility patrols," where drivers can easily see troopers along the interstates.
He said troopers have lots of duties outside traffic enforcement.
"Of course our goal would be on every road in Indiana for every person to obey the speed limit," Perrine said."Unfortunately we just don’t have the manpower to be everywhere all the time to catch all the people driving that fast."
He said anyone who speeds is putting themselves and others in danger — especially those drivers who are weaving in and out of traffic and tailgating.
I had to ask the ultimate question:Is it better to just raise the speed limit?
"You're asking for an opinion, and I can't do that," Perrine said. "I wish I could, but yeah that's a slippery slope."
Contact IndyStar transportation reporter Ethan May at emay@indystar.com or 317-402-1058.Follow him on Twitter: @EthanMayJ.
