Peak hour better than 1800 vehicles per lane per hour

[michravera]

I was looking at some traffic counts in California in order to try to answer another thread. I noticed that some sections of I-405 in LA County, California have peak hour counts that seem to get close to what I view as the theoretical maximum of 1800 vehicles per hour per lane. That would mean that the average distance between cars in less than the 2 seconds that I was taught to observe in driver training.

Are there sections of road that run significantly above this volume? Where are they and what allows them to work?

I am not interested in sections that technically have only three lanes in that directions and manage 5000 vehicles per hour because the road widens to six lanes 50 m down the road.

[jeffandnicole]

I thought the maximum was somewhere around 2,000 to 2,400 vph.

[kalvado]

I thought the maximum was somewhere around 2,000 to 2,400 vph.

2400 is a bit high. 2000-2100 in most cases, slightly better with higher speed limit

[froggie]

MnDOT has documented 2,400-ish in areas with heavy ramp metering.  I believe (though can't recall where) I've seen a 2,500 somewhere in the Twin Cities.

Don't have my HCM in front of me, but IIRC 1,800 roughly corresponds with LOS D, so there can certainly be more.

[hotdogPi]

Once you get too much traffic, the number decreases due to congestion. Are there any roads that are always busy (at least during the day), but never busy enough to slow everyone down?

[kalvado]

Once you get too much traffic, the number decreases due to congestion. Are there any roads that are always busy (at least during the day), but never busy enough to slow everyone down?

full stretch roads - probably not. Sections - easily.
I would expect any long haul highway with 10-12k/day per lane would be fairly busy, but not go into congestion mode until there is a significant reason (accident, road work etc.)
Once such highway approaches urban area (and highway has to go somewhere!) it becomes commuter-heavy, and all bets are off.

[michravera]

MnDOT has documented 2,400-ish in areas with heavy ramp metering.  I believe (though can't recall where) I've seen a 2,500 somewhere in the Twin Cities.

Don't have my HCM in front of me, but IIRC 1,800 roughly corresponds with LOS D, so there can certainly be more.

In order to get 2500 vehicles per lane in the peak hour, an entire commute hour would have to fly through with everyone following at 1.44 seconds for the entire hour. I don't know that drivers would do this much about 40 km/h.

My next question about a section of road that experiences better than 1800 vehicles per lane in the peak hour was what the average measured speed was in the slowest lane.