Rural Freeways That Need Six Lanes

[Road Hog]

Just drove I-40 between Little Rock and Memphis yesterday and it is so much worse than I remembered. There were several mile-long slowdowns simply because of the overall truck volume. The merge down to one lane approaching the I-55 multiplex was particularly bad in that regard. There had to be more trucks than cars at certain points. And I got stuck for over an hour behind what I assume was a huge accident. The new 75 mph speed limit helps, though. Three lanes in each direction can't come quickly enough.

US 70 is a good alternative.

Depending where you're coming from, US 64 between Bald Knob and Marion is also a good alternate route. Very light traffic and no trucks whatsoever, although you gotta watch out for combines during combine SZN.

[MikieTimT]

Just drove I-40 between Little Rock and Memphis yesterday and it is so much worse than I remembered. There were several mile-long slowdowns simply because of the overall truck volume. The merge down to one lane approaching the I-55 multiplex was particularly bad in that regard. There had to be more trucks than cars at certain points. And I got stuck for over an hour behind what I assume was a huge accident. The new 75 mph speed limit helps, though. Three lanes in each direction can't come quickly enough.

US 70 is a good alternative.

You must be trolling.  Alternative?  That adds an hour to the trip, and that's when there isn't farm equipment plugging up the works.  Only time I've ever been on US-70 was due to a detour brought on by an accident.

[sprjus4]

^ He's trolling.

[Avalanchez71]

Just drove I-40 between Little Rock and Memphis yesterday and it is so much worse than I remembered. There were several mile-long slowdowns simply because of the overall truck volume. The merge down to one lane approaching the I-55 multiplex was particularly bad in that regard. There had to be more trucks than cars at certain points. And I got stuck for over an hour behind what I assume was a huge accident. The new 75 mph speed limit helps, though. Three lanes in each direction can't come quickly enough.

US 70 is a good alternative.

Depending where you're coming from, US 64 between Bald Knob and Marion is also a good alternate route. Very light traffic and no trucks whatsoever, although you gotta watch out for combines during combine SZN.

US 64 is a good route through there as well.

[US 89]

Just drove I-40 between Little Rock and Memphis yesterday and it is so much worse than I remembered. There were several mile-long slowdowns simply because of the overall truck volume. The merge down to one lane approaching the I-55 multiplex was particularly bad in that regard. There had to be more trucks than cars at certain points. And I got stuck for over an hour behind what I assume was a huge accident. The new 75 mph speed limit helps, though. Three lanes in each direction can't come quickly enough.

US 70 is a good alternative.

You must be trolling.  Alternative?  That adds an hour to the trip, and that's when there isn't farm equipment plugging up the works.  Only time I've ever been on US-70 was due to a detour brought on by an accident.

He is simply horrified that Arkansas or the feds might spend one dollar towards expanding or otherwise improving I-40.

[Flint1979]

Just drove I-40 between Little Rock and Memphis yesterday and it is so much worse than I remembered. There were several mile-long slowdowns simply because of the overall truck volume. The merge down to one lane approaching the I-55 multiplex was particularly bad in that regard. There had to be more trucks than cars at certain points. And I got stuck for over an hour behind what I assume was a huge accident. The new 75 mph speed limit helps, though. Three lanes in each direction can't come quickly enough.

US 70 is a good alternative.

You must be trolling.  Alternative?  That adds an hour to the trip, and that's when there isn't farm equipment plugging up the works.  Only time I've ever been on US-70 was due to a detour brought on by an accident.

I just looked on Google Maps and put in avoid highways. This is the route they say to take from Memphis to Little Rock.

Start out on US-61 south, then take US-49 north to US-79 south to Stuttgart then take US-165 to US-70. That would add on about 50 miles and an hour and a half to the trip.

[sprjus4]

^ Well yeah, according to our expert, Avalanchez71, a route that is 2 hours longer with no congestion is reason the main route should not be addressed at all.

[webny99]

Generally, volumes on a given stretch must be above 30K in order to be considered for six-laning.

In the 4+ years since starting this thread, I've come to accept 40k AADT as the unofficial threshold for six-laning a rural freeway. Some states have widened or plan to widen segments with lower AADT volumes and/or unusually high percentages of truck traffic, but those are the exception, not the rule.

But in doing a deep dive into the Thruway, I wanted to get even more specific and come up with an hourly threshold for peak times. I came up with a very rough figure of 1800 vph per direction or 3600 vph for the entire roadway.

As an example, I-90 between Exit 44 (NY 332) and Exit 43 (NY 21) has a 2022 AADT of 43,264. Using the 3600 vph rate, the following hours qualified:

Using year-round AADT: Sun 12-4PM; Fri 2-6PM (8 hours total)
Using summer* AADT: Sun 10AM-6PM; Mon/Thurs 12-6PM; Tues/Wed 3-5PM; Fri 10AM-7PM; Sat 10AM-5PM (40 hours total)



*June 23rd-Sept 4th

[Plutonic Panda]

I disagree. Plenty of roads where the ADT might only be 15k a day but a 3 lane widening would improve safety and perhaps suffice for holiday and weekend traffic whereas most of the time it's not as packed. Still worth it. Plus I enjoy more lanes.

[JayhawkCO]

Plus I enjoy more lanes.

I enjoy them if they're necessary. If not, I much prefer a two lane road.

[kphoger]

I enjoy more lanes if people actually know how to keep right.

[webny99]

I disagree. Plenty of roads where the ADT might only be 15k a day but a 3 lane widening would improve safety and perhaps suffice for holiday and weekend traffic whereas most of the time it's not as packed. Still worth it. Plus I enjoy more lanes.

Any road with 15k AADT (7.5k per direction) does not need six lanes, even for holiday/weekend traffic. There are plenty of two-lane roads busier than that.

If you're talking 15k per direction/30k total then there is a conversation to be had, as seen in states such as Ohio and Nebraska where portions of the Ohio Turnpike and I-80 have already been widened or widening in the planning stages. For the Northeast, though, it's pointless to set the threshold as low as 30k when there are so many busier segments to consider widening first, including some over twice as busy.

[GaryV]

Still worth it. Plus I enjoy more lanes.

The question is, how much is it worth to you to enjoy more lanes? How high should the gas tax go? How much should the toll be?

[J N Winkler]

Traditionally, widenings have been considered justified if they would result in the design hour volume (traditionally defined as the 30th highest hour in the design year) being accommodated at a LOS that meets the agency's criterion for the location (Caltrans, for example, used to require LOS B in rural areas and LOS D in urban areas).  We just don't have enough holidays in the calendar for holiday traffic to influence DHV, so traffic during the peak period on a day in August is often used as a proxy for the 30th highest hour.

The 30th highest hour rule does mean that metropolitan areas with high percentages of residents who go out of town for the holidays--Los Angeles, perhaps?--tend to lose out in terms of congestion-free travel on or around those days.

[Big John]

Traditionally, widenings have been considered justified if they would result in the design hour volume (traditionally defined as the 30th highest hour in the design year) being accommodated at a LOS that meets the agency's criterion for the location (Caltrans, for example, used to require LOS B in rural areas and LOS D in urban areas).  We just don't have enough holidays in the calendar for holiday traffic to influence DHV, so traffic during the peak period on a day in August is often used as a proxy for the 30th highest hour.

The 30th highest hour rule does mean that metropolitan areas with high percentages of residents who go out of town for the holidays--Los Angeles, perhaps?--tend to lose out in terms of congestion-free travel on or around those days.

Wisconsin is cheap as they utilize the 200th highest hour instead.

[webny99]

Traditionally, widenings have been considered justified if they would result in the design hour volume (traditionally defined as the 30th highest hour in the design year) being accommodated at a LOS that meets the agency's criterion for the location (Caltrans, for example, used to require LOS B in rural areas and LOS D in urban areas).  We just don't have enough holidays in the calendar for holiday traffic to influence DHV, so traffic during the peak period on a day in August is often used as a proxy for the 30th highest hour.

Day of the week is also a factor here as well. I've found from Thruway traffic data that Fridays are typically the busiest travel day of the week, followed by the other weekend days, and then the other weekdays, with Tuesday typically being the lightest travel day.

An August Friday, for example, is likely to rank as one of the busiest travel days of the year, full stop. Meanwhile, an August Tuesday may rank as one of the busiest Tuesdays of the year, but would not rank highly among all 365 days.

The 30th highest hour rule does mean that metropolitan areas with high percentages of residents who go out of town for the holidays--Los Angeles, perhaps?--tend to lose out in terms of congestion-free travel on or around those days.

I tend to think Los Angeles is a good example, not because a particularly high percentage of residents leave town (although that may be true as well), but because the region is more or less surrounded by mountains, so high quality routes heading out of the area are limited. Any traffic leaving the metro area will generally find themselves on one of just six routes - I-5 or I-15 north, I-5 or I-15 south, US 101 north (west), or I-10 east. Contrast with NYC, which has, by my count, 14 such routes.

[CtrlAltDel]

Traditionally, widenings have been considered justified if they would result in the design hour volume (traditionally defined as the 30th highest hour in the design year) being accommodated at a LOS that meets the agency's criterion for the location (Caltrans, for example, used to require LOS B in rural areas and LOS D in urban areas).  We just don't have enough holidays in the calendar for holiday traffic to influence DHV, so traffic during the peak period on a day in August is often used as a proxy for the 30th highest hour.

The 30th highest hour rule does mean that metropolitan areas with high percentages of residents who go out of town for the holidays--Los Angeles, perhaps?--tend to lose out in terms of congestion-free travel on or around those days.

Wisconsin is cheap as they utilize the 200th highest hour instead.

I know I'm an outlier here, but I've often thought that using the 30th highest hour of traffic was a bit too much. There are, on average, 8,766 hours in a year, and going with 30 excludes only the top 0.3% of those hours. Going with the 200th highest hour excludes the top 2.2%, which seems a bit more reasonable, although I'd probably go with 5%, admittedly without access to any data, which would be somewhere around the 438th highest hour.

[J N Winkler]

I know I'm an outlier here, but I've often thought that using the 30th highest hour of traffic was a bit too much. There are, on average, 8,766 hours in a year, and going with 30 excludes only the top 0.3% of those hours. Going with the 200th highest hour excludes the top 2.2%, which seems a bit more reasonable, although I'd probably go with 5%, admittedly without access to any data, which would be somewhere around the 438th highest hour.

AIUI, the 30th highest hour has been a consensus rule since at least the 1950's (it is mentioned in Matson's Traffic Engineering, published in 1955) since it typically falls around a knee in the curve of hourly volumes plotted against hours ordered from highest to lowest.  The difference between 1st and 30th is more likely to translate into a difference in the capacity needed to maintain a given LOS than, say, between 30th and 60th.

I am aware of one project where the state DOT opted to use the 100th highest hour instead of the 30th specifically to make the planned improvement more affordable.  That was the Sterling Highway (SR 1) near Cooper Landing, Alaska, where the less stringent criterion allowed the use of two lanes with occasional passing lanes instead of four lanes divided in a tight valley.  However, the location in Alaska translates into a much greater difference between summer and winter volumes than is typically seen in more temperate climates.

The LOS criterion is another variable--the 30th highest hour with a loose standard can mean roughly the same number of hours of delay in the design year as, say, the 100th highest hour with a tight standard.

[Plutonic Panda]

Plus I enjoy more lanes.

I enjoy them if they're necessary. If not, I much prefer a two lane road.

Well, yeah, that's what I mean. I'm not advocating for more lanes just for the sake of it. I also just like bigger highways but again I wouldn't support one if it wasn't needed.

[Plutonic Panda]

I disagree. Plenty of roads where the ADT might only be 15k a day but a 3 lane widening would improve safety and perhaps suffice for holiday and weekend traffic whereas most of the time it's not as packed. Still worth it. Plus I enjoy more lanes.

Any road with 15k AADT (7.5k per direction) does not need six lanes, even for holiday/weekend traffic. There are plenty of two-lane roads busier than that.

If you're talking 15k per direction/30k total then there is a conversation to be had, as seen in states such as Ohio and Nebraska where portions of the Ohio Turnpike and I-80 have already been widened or widening in the planning stages. For the Northeast, though, it's pointless to set the threshold as low as 30k when there are so many busier segments to consider widening first, including some over twice as busy.

It all depends on the situation in my opinion.

[US 89]

Maybe if money grew on trees...

[Plutonic Panda]

Maybe if money grew on trees...

True.

[GaryV]

Maybe if money grew on trees...

True.

It does, right? Money is made of paper, and paper comes from trees.   

[Big John]

Maybe if money grew on trees...

True.

It does, right? Money is made of paper, and paper comes from trees.   

nope.  25% linen and 75% cotton.

[CtrlAltDel]

I know I'm an outlier here, but I've often thought that using the 30th highest hour of traffic was a bit too much. There are, on average, 8,766 hours in a year, and going with 30 excludes only the top 0.3% of those hours. Going with the 200th highest hour excludes the top 2.2%, which seems a bit more reasonable, although I'd probably go with 5%, admittedly without access to any data, which would be somewhere around the 438th highest hour.

AIUI, the 30th highest hour has been a consensus rule since at least the 1950's (it is mentioned in Matson's Traffic Engineering, published in 1955) since it typically falls around a knee in the curve of hourly volumes plotted against hours ordered from highest to lowest.  The difference between 1st and 30th is more likely to translate into a difference in the capacity needed to maintain a given LOS than, say, between 30th and 60th.

Thanks for this and the rest of your contextualization here, in particular the wiggle room afforded. But still, again on my own personal level, I'm not really sold on the idea that the highest level of traffic the road gets in normal use is the best conceptual norm to have. Accepting some overcapacity issues for 5% of the time, as I arbitrarily placed it, is more reasonable.

That said, as you point out, that may not matter all that much. The charts I've looked at online show a pretty gently rising slope up to that 30th hour. I haven't found any, though, that go further back than the 200th hour or so, so who knows what's down there.