Merging lanes > mainline lanes

[Kniwt]

While transitioning earlier today from I-205 to I-5 near Tracy, Calif., I was hit with the trivia bug.

After the recent I-205 widening project, we now have the case where three lanes of I-205 merge with the two mainline lanes of I-5 at the end of I-205:
http://maps.google.com/maps?client=safari&q=i-5+and+i-205,+tracy+ca&oe=UTF-8&ie=UTF8&hl=en&hq=&hnear=Interstate+5+%26+Interstate+205,+Tracy,+San+Joaquin,+California+95304&ll=37.77508,-121.320694&spn=0.001454,0.002607&t=k&z=19

I'm trying to think of other freeway junctions where this condition exists (surely it does, and quite probably in California), but I'll bet y'all will come up with them far more quickly than I would.

[Brandon]

At the I-55/I-355 interchange in Bolingbrook, IL, three lanes come in from Nbd and Sbd I-55 and add to the three lanes of I-355 Nbd.  One ends, one exits to Boughton Rd, and one goes to the Boughton Rd Toll Plaza.

At the I-355/I-290 interchange in Itasca, IL, three lanes of Nbd I-355 merge with two lanes from Wbd I-290 to become I-290 Wbd.  A similar condition exists on Ebd I-290 whereby I-355 Sbd gets three lanes and Ebd I-290 gets two lanes.

[Ace10]

Well, if you could count the western terminus of I-12, the same thing kinda sorta happens there. Three lanes of I-12 westbound merge onto two lanes of I-10 going westbound. I-10 is arguably the more major route, even though both interstates are technically two-digit.

Edit: Though the recent construction in Baton Rouge will probably add at least another lane to I-10, so this may not exist in the near future.

[vtk]

West end of I-670 in Columbus: two lanes of I-670 join (from the left) two lanes of I-70. However, I-670 is 3 lanes until just before reaching I-70, and it's apparent from the excess pavement that it was originally designed to stay 3 lanes all the way to an "inside merge" with I-70, which would mirror the EB split. http://maps.google.com/?ie=UTF8&hq=&hnear=Columbus,+Franklin,+Ohio&ll=39.969835,-83.068013&spn=0.005756,0.010933&t=k&z=17

[english si]

They've narrowed The M1/M6 merge so that the mainline M1 goes down to 2 lanes just before the merge, with the 3-lane M6 merging in with it to form 3 lanes. Really it should be 2+2 into 3 (if you are keeping the road south as 3 lanes) and will probably be when they rebuild the junction.

The far better M3 mainline-M25 sliproads merge (the temporary layout when the google car came along is now permanent), where 2 lanes from the M25 merge with the 1-lane mainline. This works as most traffic joins the motorway here. A similar 2-lane sliproad merging in with a one-lane mainline happens here at the Blackpool end of the M55.

[vtk]

I just remembered: 1 lane of SB OH-315 is joined by 3 lanes entering from I-270 near Worthington, and IIRC 1 lane of EB OH-161 is joined by 3 lanes entering from I-270 & Sunbury Rd. In both cases, the mainline narrows from 2 lanes just before the entrance lanes join it.

[Duke87]

The southbound Hutchinson River Parkway at exit 15 has 4 lanes which split into 3 exiting onto the Cross County Parkway and only 2 staying on the Hutch.
Northbound, though, the Cross County narrows to 2 lanes before the merge, so it's 2+2 into 4... so this example only holds on the diverging side, not the merging side.

For a merging example, the 1st Street exit off I-280 in New Jersey westbound has 2 lanes of 280 merging with 3 lanes coming from surface streets!

[citrus]

In Rhode Island, 3 lanes of NB RI 4 merge into 2 lanes of NB I-95.

[ftballfan]

I-96 westbound at the Alpine Ave interchange is the same way. After the right lane leaves, WB I-96 drops to one lane for a short while. Then two lanes merge in on the left from a ramp from NB US-131 to WB I-96 (said ramp is the main way from Grand Rapids to Lake Michigan, a very popular summer destination).

[vdeane]

NY 590 south where lanes from NY 104 west merge in.  Two lanes from NY 104, one from NY 590 (which promptly ends; before complaints, it ended right there with no time to merge in, so for about a month there were arguably 0 lanes from NY 590 merging into two from NY 104!); from NY 104 two go to NY 590 and one stays with NY 104 (OK, there's technically two, but the second starts here and ends as an exit only lane for Culver Rd after two merge in from NY 590 north).

[Alps]

NJ 3/US 46 is currently a balanced 2/2 split, but NJ 3 immediately opens up to 3 lanes each way. In the near future the interchange will be reconstructed so that the merging NJ 3 has more lanes than the through US 46 each way. (In other words, it'll be a 2/3 split like it ought.)

[mapman]

I'm trying to think of other freeway junctions where this condition exists (surely it does, and quite probably in California), but I'll bet y'all will come up with them far more quickly than I would.

Off hand, I can think of two California examples:

1. Northern I-5/I-805 interchange in San Diego -- Northbound, five I-805 lanes merge into four I-5 lanes, while southbound four I-805 lanes split off from three I-5 lanes. (These lane totals exclude the bypass lanes.)

2. I-580/I-238 interchange in Hayward -- three lanes exit for westbound I-580, two for northbound I-238; three lanes from eastbound I-580 merge onto two from southbound I-238

There are probably more...

[1995hoo]

The Springfield Interchange in Virginia is somewhat of a special case in this respect because I-95's thru lanes use flyover ramps through the interchange and in the eyes of just about everyone who drives through there, the two mainlines are the I-95/I-395 connection and the Capital Beltway and everything else involves exiting (including staying on I-95 because you're exiting the wider mainlines onto two-lane flyovers). In the eyes of VDOT, every move that doesn't involve using the I-95 flyovers entails an "exit," and I understand their thought process, but almost nobody who drives there thinks of it that way. In any event, you have the following sorts of merges:

(1) Eastbound on the Beltway (I-495) four lanes of the Beltway are joined by two lanes of I-95 descending from the flyover on the left, although one of the I-495 lanes is dropped a short distance to the east and then another becomes Exit-Only for the next interchange.

(2) Going south on I-95 over the flyover, the two lanes from the flyover join four lanes coming from I-395; the I-395 lanes themselves consist of two thru lanes from I-395 and a two-lane ramp from the Beltway that's marked for I-95 South. (The barrier-separated exit carriageway for Springfield consists of five lanes and is wider than the southbound carriageway.)

(3) The three-lane flyover from northbound I-95 to northbound I-495 (Beltway towards Tysons Corner) merges with a ramp from southbound I-395 to the Beltway and the combined ramp briefly has five lanes, though it narrows to four before merging with the four-lane Beltway.

If you adopt VDOT's view that not staying on I-95 constitutes an "exit," then you have a three-lane "exit" from I-95 where the Inner Loop (westbound) of the Beltway goes straight ahead and the ramp to Springfield splits off to the right; you also have a three-lane I-395 as an "exit" to the right from the two-lane I-95 entering the northbound flyover. (Most people I know feel that the I-395 "exit" is legitimate but that calling the three thru lanes on the Beltway an "exit" stretches credibility.)

[roadman65]

How about Fort Lee, NJ on SB I-95 Local Lanes from the Upper Level of the GWB?  The main lanes go for NJ 4 while I-95 gets one lane from there until it merges into the Lower Level Local lanes.  It seems like you exit I-95 temporarily to use NJ 4 and then get back onto I-95 as the one lane road is really a ramp.

[2Co5_14]

Near Smyrna, GA (northwest of Atlanta), the 3 lanes of northbound I-75 join with 4 lanes coming from the I-285 ramps.  Just past this point, 2 more lanes join coming from the Windy Hill Rd onramp, for a total of 9 northbound lanes! (at least for a short distance.)

[agentsteel53]

1. Northern I-5/I-805 interchange in San Diego -- Northbound, five I-805 lanes merge into four I-5 lanes, while southbound four I-805 lanes split off from three I-5 lanes. (These lane totals exclude the bypass lanes.)

does this count given that 805 ends there?  In that case, there would be many other examples where the freeway ended at a merge.

5 at 8 is an example where neither freeway begins.  8 mainline eastbound drops to one lane, and two lanes come in from the left which departed 5 southbound.

[myosh_tino]

While transitioning earlier today from I-205 to I-5 near Tracy, Calif., I was hit with the trivia bug.

After the recent I-205 widening project, we now have the case where three lanes of I-205 merge with the two mainline lanes of I-5 at the end of I-205:
http://maps.google.com/maps?client=safari&q=i-5+and+i-205,+tracy+ca&oe=UTF-8&ie=UTF8&hl=en&hq=&hnear=Interstate+5+%26+Interstate+205,+Tracy,+San+Joaquin,+California+95304&ll=37.77508,-121.320694&spn=0.001454,0.002607&t=k&z=19

I'm trying to think of other freeway junctions where this condition exists (surely it does, and quite probably in California), but I'll bet y'all will come up with them far more quickly than I would.

...and before I-205 was widened, it was the other way around.  The 2 lanes from I-205 merged with the 3 lanes on I-5.

I found it interesting that Caltrans decided to reduce I-5 from 3 lanes to 2 just before the I-205 merge which makes for this odd situation.  Northbound I-5 widens to 3 lanes at the BL-205 overcrossing by adding a new *left* lane but less than a mile later, I-5 narrows back to 2 lanes with the *right* lane ending.  If this was a heavily traveled section of freeway (for the most part, it is not), then that configuration could lead to a lot of weaving.

[realjd]

1. Northern I-5/I-805 interchange in San Diego -- Northbound, five I-805 lanes merge into four I-5 lanes, while southbound four I-805 lanes split off from three I-5 lanes. (These lane totals exclude the bypass lanes.)

Except there, none of the NB I-5 lanes continue. The 5 merges onto itself.

[kj3400]

Well there's the example where I-70 WB soars over I-695 with one lane and joins with 3 lanes of from I-695 traffic. There's also where I-695 OL's two lanes join MD 702's one lane.

[mukade]

I-70 exits a total of four lanes on to three through lanes of northbound I-465 (east leg) in Indianapolis.

Google Maps I-465 at I-70

[shadyjay]

NYC area:

I-95 NB leaving the NJ Turnpike N/S alignment and merging into the local and express lanes of I-80 to head towards the GWB.  Two lanes merge into one just before the roadway drops down into the express/local lanes from I-80.

I-95 NB as it departs the Cross Bronx Expy goes to 2 lanes, then a single lane, to merge into 3 lanes coming off the Bruckner Expy as I-278 ends.  Same condition exists SB.

I-87/I-287 NY Thruway Interchange 8.  Before the reconstruction, I-287 exiting I-87 SB had a single exit only right lane.  Now I-287 gets 3 lanes while I-87 SB gets 2 lanes. 


New England:

I-95 NB in Dedham MA dropping down to 2 lanes at Exit 12 and a single lane loop ramp as it drops down to join the Yankee Division Highway (MA 128), which is 3 lanes at that point (soon to be 4 lanes).  Later in Peabody, I-95 'exits' from itself at Exit 45, 2 lanes to the right while the mainline gets 3 lanes (MA 128 North).  SB at the same junction 2 lanes of I-95 merge into 3 lanes of MA 128. 

[ftballfan]

Northbound US-31 in Muskegon may qualify as an example. At the I-96 interchange, US-31 is two lanes NB. One lane comes in from I-96 WB (it looks wide enough for two lanes) and another lane comes in from Airline Rd. Here, four (or five) lanes merge into two.