When did the cloverleaf fall out of fashion?

[CapeCodder]

In the early days of the Interstate System, cloverleaves were almost everywhere. Now they're becoming rarer and rarer. When did we as a road building society reach the point where we said "You know, these things are pretty damn dangerous. We should probably look into studying other types of interchanges."?

[silverback1065]

They're dangerous and terrible in urban areas. Weaving issues make them dangerous and cut their ability to handle high amounts of traffic. They also take up too much space in urban areas too. Parclos are so much better. Cloverleaf's are hot garbage in urban areas, but they're fine in rural areas. Not sure when we started to realize this but that's largely why they're not popular anymore.

[CapeCodder]

They're dangerous and terrible in urban areas. Weaving issues make them dangerous and cut their ability to handle high amounts of traffic. They also take up too much space in urban areas too. Parclos are so much better. Cloverleaf's are hot garbage in urban areas, but they're fine in rural areas. Not sure when we started to realize this but that's largely why they're not popular anymore.

In my part of MA, we use the Parclo quite liberally. We do have one full cloverleaf: Exit 9 on the Mid-Cape. From there the MC is a Super 2 known as Suicide Alley. The next three exits are parclos. Off Cape, the nearest clover is on 195 and is the exit to Marion.

[silverback1065]

My definition is offsetting loops so their movements don't interfere. Think exit 33 on I-465 in Indianapolis.

[RobbieL2415]

There are only a handful of cloverleafs in CT and they're all substandard.

[wanderer2575]

Seems obvious they fell out of favor as traffic volumes and thru traffic speeds increased, making weave/merge movements with thru traffic more hazardous and disruptive.  Note that cloverleafs are still generally acceptable with collector/distributor lanes, which have no effect on the volume of weave/merge movements but eliminate the thru traffic.

[Ned Weasel]

They're dangerous and terrible in urban areas. Weaving issues make them dangerous and cut their ability to handle high amounts of traffic. They also take up too much space in urban areas too. Parclos are so much better. Cloverleaf's are hot garbage in urban areas, but they're fine in rural areas. Not sure when we started to realize this but that's largely why they're not popular anymore.

This one seems to work just fine despite the oddly shaped ramps and low-speed geometry, but these highways are signed at 45 MPH, not 55 or greater: https://goo.gl/maps/6pCMX8BSFabdU3h1A

If there's one reason I'd change it, it would be to improve pedestrian access, because that's hard to do right now without the expense of building pedestrian overpasses.

In general, I think cloverleaves on higher-speed roads are fine if you add C-D lanes, except when one of the left-turning movements has a significantly high volume and is unduly burdened by going through the weaving/loop path.  But if you want one of the roads to have good pedestrian/bicycle access, I'd go with a diamond, SPUI, diverging diamond, roundabout diamond, folded diamond, or maybe a parclo depending on how you handle the free-flowing geometry.

[Henry]

They're dangerous and terrible in urban areas. Weaving issues make them dangerous and cut their ability to handle high amounts of traffic. They also take up too much space in urban areas too. Parclos are so much better. Cloverleaf's are hot garbage in urban areas, but they're fine in rural areas. Not sure when we started to realize this but that's largely why they're not popular anymore.

Try telling that to IL! I-80 alone has at least four of them: at I-55 in Joliet is still a cloverleaf, at I-39 near Lasalle, and at I-280 and I-88 east of the Quad Cities.

[cbeach40]

They're dangerous and terrible in urban areas. Weaving issues make them dangerous and cut their ability to handle high amounts of traffic. They also take up too much space in urban areas too. Parclos are so much better. Cloverleaf's are hot garbage in urban areas, but they're fine in rural areas. Not sure when we started to realize this but that's largely why they're not popular anymore.

FTFY 

Not nitpicking, just saying I wouldn't even qualify it with urban vs rural. Weaving is *the* problem in any setting, just the busier the highway the more amplified the problem is. A very large portion on my transportation engineering course back in college was dedicated just to dealing with it. Causes breakdowns in throughput and dramatically increases collision rates.

There's a lot of variation as to when it fell out of favour. Here in Ontario we last built one in about 1964. Other jurisdictions have built them into the 21st century. But yes, their day is definitely done.

[TheHighwayMan3561]

Hello from merry old Ireland, where we've got lucky clovers for anyone and everyone! Oprah says you get a cloverleaf, and YOU get a cloverleaf, and even YOU TOO can have a cloverleaf!

[jmacswimmer]

Maryland has done quite a bit of de-cloverleafing over the years to eliminate the weaving problem, in particular along the beltways. Here's some examples of interchanges that are now parclos:

I-495: exit 3 (done as part of the WWB replacement project), exit 7 (in this case, replaced a cloverleaf with a turbine flyover ramp), exit 15, exit 17, exit 19 (in this case, upgraded to a turbine interchange with 1 remaining cloverleaf), exit 20 (which also helps explain this phantom gantry), exit 25, exit 29, exit 31 (the remaining 3/4-cloverleaf still leaves a lot to be desired), exit 33

I-695: exit 15, exit 18, exit 26, exit 27, exit 31

There's also 2 unusual cases at I-70 exit 87 & I-83 exit 20: For the US 29 NB->I-70 WB and Shawan Rd WB->I-83 SB movements, traffic can either take the original cloverleaf ramp or use a left-turn across the opposing direction, which then puts them on the ramp coming from that opposite direction.  My guess is that these were both done so that traffic can make these movements from either side of the road, and not have to squeeze all the way to the right to take the cloverleaf.

Are other states as big into de-cloverleafing as MD is?

[jeffandnicole]

Regarding the creation of the cloverleaf: The 1st cloverleaf was constructed in NJ, well before limited access highways were built.

You know what else was basically a NJ invention - the traffic circle (NJ inventing it is an exaggeration, but they certainly went all in with them).

And another often used function in NJ: The jughandle.

If you notice the similarities above: NJ wanted to keep traffic flowing, with minimal causes for stoppage.  But, as was noted above, these traffic control functions also take up a lot of real estate.  Many interchanges either don't need to have continuous traffic flow on the cross street, or there's too much traffic on either roadway that would overpower a cloverleaf.  Weaving is always an issue, and along with that is the natural substandard accel/decal lanes cloverleafs provide within that weaving movement.

Even NJ tended to build cloverleafs where it made more sense.  Using South Jersey for an example, while NJDOT had to plow thru NJ 42, I-76 & I-295 into the older existing Philly suburbs, full cloverleaf interchanges aren't found in those older suburbs.  Only as you travelled further away from those older suburbs would you start finding cloverleaves, such as where 295 meets 70 & 73.  NJ 42 doesn't feature any full cloverleaf interchanges.

Most states don't consider cloverleafs for their interchanges, or they are so far down the list of options they would only get looked at if there's issues with their preferred designs.  Nothing wrong with that - while it's good to consider options, there's nothing that requires every available option to be considered.

Because NJ isn't really building highways anymore, there aren't many new cloverleafs in the state. However, it's not for the lack of trying.  When they review intersections to be upgraded to grade-separated interchanges, cloverleafs are still considered, and then accepted or rejected based on engineering studies and traffic projections.  Jughandles are more likely where you're going to find some sort of cloverleaf being built in the state.

[webny99]

I think the question isn't so much "When did cloverleaves fall out of fashion?" It's more "When did C/D roads become the fashion?"

[1995hoo]

Maryland has done quite a bit of de-cloverleafing over the years to eliminate the weaving problem, in particular along the beltways. ...

Are other states as big into de-cloverleafing as MD is?

VDOT is in the process of modifying two of I-395's partial cloverleafs, the ones at Duke Street and Edsall Road. Both were already more like three-quarter cloverleafs in that the movement from the eastbound arterial to northbound I-395 that would normally be accomplished via a loop ramp in the cloverleaf's southeastern quadrant was replaced with a flyover ramp. Problem was, the southbound side of I-395 suffered from the lack of C/D roads. At Duke Street, VDOT has removed the loop-around exit ramp from southbound I-395 to eastbound Duke Street (southwest quadrant of interchange) and modified the other southbound exit ramp such that you now exit and then either head west on Duke Street or turn left at a new traffic light to head eastbound; they've also created a lengthy new approach road such that traffic entering from Duke Street (at least from eastbound Duke Street) now joins I-395 via the existing Turkeycock ramp serving as a way out of the express lanes. The Edsall Road interchange just south of there has been modified by removing the loop-around ramp from westbound Edsall to southbound I-395 such that instead you turn left at a new light. In both cases, eliminating one of the loop ramps eliminates a weave area in the rightmost thru lane of southbound I-395.

[kkt]

My impression is that very few new cloverleafs were built after the mid 1960s.

[froggie]

My impression is that very few new cloverleafs were built after the mid 1960s.

I can think of a number of examples built since 1980:

- I-35E/MN 77 (albeit with C/D roads in 35E)
- MN 13/MN 77
- I-35/US 14
- US 169/MN 610
- US 24/US 31
- US 45/US 84 (albeit with C/D roads on 84)
- I-55/I-69/I-269 (albeit with C/D roads on 55)
- I-22/I-269/US 78 (albeit with C/D roads)
- Many of the interchanges along VA 288
- Most of I-664 in Suffolk, VA

Some of these were built after 2000.

[webny99]

My impression is that very few new cloverleafs were built after the mid 1960s.

I would add a caveat: very few new interstate to interstate cloverleafs, especially in urban areas.

[skluth]

They're dangerous and terrible in urban areas. Weaving issues make them dangerous and cut their ability to handle high amounts of traffic. They also take up too much space in urban areas too. Parclos are so much better. Cloverleaf's are hot garbage in urban areas, but they're fine in rural areas. Not sure when we started to realize this but that's largely why they're not popular anymore.

Try telling that to IL! I-80 alone has at least four of them: at I-55 in Joliet is still a cloverleaf, at I-39 near Lasalle, and at I-280 and I-88 east of the Quad Cities.

Don't know about the Quad Cities interchanges. The I-39 interchange works pretty good, but it's in the middle of nowhere. The I-55 interchange needs to be redesigned to at least eliminate the cloverleafs from I-80 to I-55. The I-55 to I-80 cloverleaf ramps don't seem to be as busy, and removing the two cloverleafs would allow longer deceleration lanes along I-55 and longer acceleration lanes along I-80 for the remaining cloverleaf ramps.

[Ned Weasel]

Regarding the creation of the cloverleaf: The 1st cloverleaf was constructed in NJ, well before limited access highways were built.

You know what else was basically a NJ invention - the traffic circle (NJ inventing it is an exaggeration, but they certainly went all in with them).

And another often used function in NJ: The jughandle.

There's also the at-grade cloverleaf intersection, which is basically a hybrid between a cloverleaf and a set of jughandles.

[formulanone]

My impression is that very few new cloverleafs were built after the mid 1960s.

Florida used them in bunches for throughout their interstate binge of the 1970s and early-1980s.  Lots of fresh right-of-way. Loads of parclos also remain...yay for 25 mph traffic trying to merge in with overzealous right-lane passers!

[Amtrakprod]

Good, it's about time we get rid of those weaving nightmares. Don't know why we used them in the first place.

[zzcarp]

CDOT has done a reasonable job eliminating cloverleafs. One that remains is Exit 2 on I-270 with US 6-85 in Commerce City. That one is hot garbage-from 6 to 9 in the morning and 2-7 in the afternoon will always see congestion. Too many trucks slowing down to exit to/from the industrial areas.

[sprjus4]

My impression is that very few new cloverleafs were built after the mid 1960s.

I can think of a number of examples built since 1980:

- I-35E/MN 77 (albeit with C/D roads in 35E)
- MN 13/MN 77
- I-35/US 14
- US 169/MN 610
- US 24/US 31
- US 45/US 84 (albeit with C/D roads on 84)
- I-55/I-69/I-269 (albeit with C/D roads on 55)
- I-22/I-269/US 78 (albeit with C/D roads)
- Many of the interchanges along VA 288
- Most of I-664 in Suffolk, VA

Some of these were built after 2000.

A few in North Carolina in the past couple decades -
- I-95 / I-795 / US-264 (C/D roads on I-95) - around 2006
- US-264 / NC-11 Bypass - 2019
- US-70 / US-17 (only partially in use, stub on north side) - around 2012
- I-95 / I-74 (C/D roads on I-95) - around 2008
- US-1 / US-421 (C/D roads on US-421) - around 2008
- I-85 / I-73 (C/D roads on both) - around 2006
- I-85 / US-421 (C/D roads on both, one flyover) - around 2006

In Chesapeake, VA, the I-64 / VA-168 Business (Battlefield Blvd) interchange was originally a smaller cloverleaf. Around 2008, the entire interchange was reconstructed with a new, wider cloverleaf with new C/D roadways on I-64, and a new overpass.

[jeffandnicole]

My impression is that very few new cloverleafs were built after the mid 1960s.

Florida used them in bunches for throughout their interstate binge of the 1970s and early-1980s.  Lots of fresh right-of-way. Loads of parclos also remain...yay for 25 mph traffic trying to merge in with overzealous right-lane passers!

This is why keeping to the right except to pass is important.  For some reason, the slower vehicle drivers think they are safer in the middle lanes, which in fact they are causing many of the safety issues on the highway.

[formulanone]

This is why keeping to the right except to pass is important.  For some reason, the slower vehicle drivers think they are safer in the middle lanes, which in fact they are causing many of the safety issues on the highway.

Yes, the slowest traffic mostly belongs in the right-most lane.

I think in (mostly urban) places where there's a lot of exits spaced out every mile (or less), it's understandable to not hang out there if you're at least doing the speed limit, if there's several lanes of travel.