[gascan]

Do you have a source for that? I had always understood the speed limit as simply being an objective, statutory codification of the subjective notion of "appropriate maximum speed for conditions"

Which fits well with dynamic speed limits cropping up in places that get regular bad weather

[bsagdiyev]

https://leginfo.legislature.ca.gov/faces/codes_displaySectio....

There is the source for California -- I see it gives exemptions for safety and law (I assume for road works, etc) but generally speed limits are objective based on conditions. It doesn't mean you can drive slow and impede other traffic traveling around you though, which is why there are laws for it. I don't see it enforced as much in San Diego, but when I lived in the Lake Arrowhead area it was enforced quite often on the highway up and down the mountain.

Quick edit -- that law is for highways, I haven't checked whether this also applies for other types of roads.

[dragonwriter]

> Quick edit -- that law is for highways, I haven't checked whether this also applies for other types of roads.

Note that “highway” in California law has a very broad definition; see https://leginfo.legislature.ca.gov/faces/codes_displaySectio....

“Highway” is a way or place of whatever nature, publicly maintained and open to the use of the public for purposes of vehicular travel. Highway includes street.

[bsagdiyev]

Thanks for that, I wasn't aware of how broad the term was for California. Do you know if (silly question I'm sure) that definition can differ per county or municipality?

[thinkharder]

I started to reply to thinking there was a federal minimum speed limit but decided I should confirm what I believed and glad I did because I was wrong. In the US, states have full control over the speed limits that are set on both the state hwys and the interstate freeways within that state. That said, I'm pretty sure every freeway I've ever been on had a posted minimum 45mph speed limit, and bikes are not allowed.

Whether or not speed variances between vehicles increase accidents doesn't seem to be clear. With a quick search I found this(1) that indicates that speed variances don't play a role in causing accidents. I also found this (2), which says "that the greater the difference between a driver’s speed and the average speed of traffic—both above and below that average speed—the greater the likelihood of involvement in a crash". And I found this (3) which basically says the speed limit should be set at the 85th percentile of what everyone is driving. Kind of like how you should build sidewalks where people walk ("Don’t make any walkways this year. At the end of the year, look at where the grass is worn away. That shows where the students are walking. Then just pave those paths"), set the speed limit at the speed most people drive.

Everywhere in the US I've lived, the max speed limit laws were written like "whatever speed is safe for current conditions up to a maximum of XX Mph" So you can get a speeding ticket for going slower than the posted limit if conditions are bad. I've actually been pulled over going well under the posted max speed limit during a hard snow storm.

(1) https://www.caee.utexas.edu/prof/kockelman/public_html/TRB04... (2) https://en.wikipedia.org/wiki/Solomon_curve (3) http://onlinemanuals.txdot.gov/txdotmanuals/szn/determining_...

[ghaff]

>That said, I'm pretty sure every freeway I've ever been on had a posted minimum 45mph speed limit, and bikes are not allowed.

There are exceptions, especially in the US West, where interstates may be the only path for miles and miles through some mountain ranges. Of course, they mostly have wide shoulders where people ride.