Here's Everything You Ever Needed To Know About Speed Limits

Surely you knows you’re supposed to follow posted speed limits, but do you know how they’re set in the first place?


A lot goes into setting speed limits, even if there’s some disagreement over how the standard process works—which I detailed last month. If you want a quick refresher, though, here’s a video that breaks down the basics.

Go forth now with your knowledge of road signs.

Senior Reporter, Jalopnik/Special Projects Desk


PotbellyJoe and 42 others

This is my sign on I-80/90 headed west from the OH border, just after the toll booths.

Ever since I started making the trip between Kalamazoo and New Jersey I noticed that leaving the toll booths entering Indiana there was no sign to indicate the speed limit. The sign before the booths says 45 in preparation for stopping. So by that rule, the police had always held that the road between the toll booths and I-69 was 45 mph, as there were no on ramps prior to the next 70 MPH sign, every driver last saw a 45 mph speed limit. My grandmother has even received a ticket for speeding at 65 mph through there. So what happened to make this my sign?

Doing ~45 when traffic around you is doing north of 70 never felt safe, but doing 70 in a 45 was a huge ticket if that was the law. This was a no win. So I did what I could. I sent an email to the Indiana Department of Transportation’s manager of the ITR asking for information as it had bothered me for years. He responded quickly and cordially:

Unless posted otherwise, the speed limit on the Indiana Toll Road is 70 miles per hour (mph) for motor vehicles having a declared gross weight of not more than twenty-six thousand (26,000) pounds. Vehicles over twenty-six thousand (26,000) have a maximum limit of 65 mph unless they are “oversized” and those vehicles are 55 mph unless otherwise posted. Typically speed limits are reduced approaching toll road barriers, construction or work zones and in other urban areas on the western portion of the Indiana Toll Road.

So it would be safe to assume that this section would be 70 mph, except for the clause of “unless otherwise posted.” Remember that going into the tolls, it’s 45 and there are no signs after to the contrary until after the first exit; I-69.

Thankfully, the ITR Manager at INDOT sent my query to the Chief Engineer who oversees the everyday maintenance of the ITR and he forwarded my question internally to the people who could help. I will say, for all intents and purposes, I never expected a response to my question. I really just sent it to get it off of my chest.

Later, I received an email from the ITR Public Relations Manager stating that I had found something that had never been noticed in 30+ years. There is no sign between Eastpoint and Angola because there is no entrance ramp between Eastpoint and Angola.

Hi Mr. [Potbelly],

[The Chief Engineer] passed your message onto me so I could coordinate with some different departments to address your question.

Interestingly, you picked up on something that people who have been working here for 30+ years hadn’t noticed: There is not a 70/65 mph speed limit sign westbound after the Eastpoint plaza until Angola, as you observed. Upon reviewing our sign inventory on the road, we have posted speed limit signs placed after each entry ramp and mainline toll plaza … except for Eastpoint.

As [The INDOT Manager] stated previously, the speed limit is 70 mph for passenger vehicles and 65 mph for heavy trucks, and approaching and leaving mainline toll plazas it becomes 45 mph. There is a technicality here, because the westbound speed limit does become 70 mph (for passenger cars) about a quarter of a mile after the Eastpoint plaza; however since the previous westbound posted speed limit sign after the Eastpoint plaza is 45 mph, the State Police could technically enforce that speed limit as it’s the last posted sign.

So to address this issue of missing signage, we will be installing posted 70mph/65mph speed limit signs as soon as possible. Our maintenance department is working on the project submission, and in the future having those installed will clear up any ambiguities as to speed limits in that area.

Please let me know if you have further questions, and I’d like to extend our gratitude for you pointing out this issue.

Thanks again,


So it was always supposed to be 70 mph, but due to an oversight of no entrance ramps it has remained 45. Thanks to my inquiry, they corrected it. I asked if I could claim the sign as mine and the PR manager laughingly said yes, I could call it, “my sign.”