Lets talk about the Squirrel Hill Tunnels (Pittsburgh, Churchill: to live in, design)

[gallacus]

Originally Posted by youngabe

I hope I'm wrong, but I just don't see how this is going to help congestion at all, even once complete. From someone who drove the inbound and outbound Parkway East at rush hour (keyword) for years--the congestion doesn't necessarily come from the tunnel at peak times during the week. Inbound, you see a lot of congestion from Churchill to Edgewood/Swissvale because of all traffic merging in from the poor on-ramps, well before the tunnel. Anyone who has driven the morning rush knows that once you get past the last on-ramp and you're on the approach to the tunnel, you easily get up to 45 mph or better...proving, it isn't the tunnel...during the week. MOST of those drivers are used to the tunnel and don't randomly break.

I have to say, I've been driving through these tunnels for 6 years, and have noticed the exact same thing. I've long thought the whole "people break in the tunnel" thing to be a myth. It seems that every tunnel has ridiculous merge points immediately before and after the entrances and exits respectively, and this is what causes the traffic tie-ups, not some psychological effect.

[mjost7]

It is both. There is the natural lower capacity of the tunnels, and the higher demand from the ramps. And you are right, the slowing down happens just outside of the tunnels. The tunnels themselves would operate at about capacity, say maybe around 35 or 40 mph.

If there is a scenario, for instance, where there isn't much demand from the ramps near the tunnels but I-376 mainline is fairly dense with traffic, you'd still get a back up starting outside of the tunnel.

[TechieTransplant]

Originally Posted by gallacus

I have to say, I've been driving through these tunnels for 6 years, and have noticed the exact same thing. I've long thought the whole "people break in the tunnel" thing to be a myth. It seems that every tunnel has ridiculous merge points immediately before and after the entrances and exits respectively, and this is what causes the traffic tie-ups, not some psychological effect.

I don't know how ridiculous the merge points are. I used to work in the South Hills, and don't find it difficult at all, just as don't find the on ramp at Edgewood/Swissvale hard. People simply panic because of the high traffic volume they are approaching.

[gg]

Go through any tunnel anywhere and people slow down. Well maybe not in the NYC area, but most places. All it takes is one person to feel uncomfortable and that dominos for a long time through the tunnels. It is what it is.

[SammyKhalifa]

Originally Posted by h_curtis

Go through any tunnel anywhere and people slow down. Well maybe not in the NYC area, but most places. All it takes is one person to feel uncomfortable and that dominos for a long time through the tunnels. It is what it is.

And then what happens is that the individuals in the tunnel get to throw their hands up in the air and feel superior because of how everyone going through the tunnel is stupid and a bad driver except for them.

[jay5835]

Originally Posted by h_curtis

Go through any tunnel anywhere and people slow down. Well maybe not in the NYC area, but most places.

I guarantee you people slowed down going through the Holland and Lincoln Tunnels.

[BrianTH]

As I've noted before, inbound on the Squirrel Hill tunnel I have frequently experienced traffic speeding up a bit once we are past the merge from the Edgewood/Swissvale on ramp, only to have it slow down again as it gets closer to the tunnel. It seems to me that is good evidence behavior related to the tunnel itself is indeed at least contributing to the problem.

[SammyKhalifa]

Originally Posted by BrianTH

As I've noted before, inbound on the Squirrel Hill tunnel I have frequently experienced traffic speeding up a bit once we are past the merge from the Edgewood/Swissvale on ramp, only to have it slow down again as it gets closer to the tunnel. It seems to me that is good evidence behavior related to the tunnel itself is indeed at least contributing to the problem.

I don't know about Squirrel Hill; but I am sure that one of the main problems at Ft Pitt is that the road branches out in about eight different directions on the other side, and people are unsure of where to go or what lane to be in.

[WestLibertyAve]

Originally Posted by SammyKhalifa

I don't know about Squirrel Hill; but I am sure that one of the main problems at Ft Pitt is that the road branches out in about eight different directions on the other side, and people are unsure of where to go or what lane to be in.

With the Ft. Pitt inbound I think it's more the criss-crossing traffic before the tunnel at the Banksville merge point and Rt. 51 exits that causes a lot of the slowdowns.

[WestLibertyAve]

Originally Posted by h_curtis

Go through any tunnel anywhere and people slow down. Well maybe not in the NYC area, but most places.

There are inbound toll booths at those tunnels, so there's always a massive traffic jam waiting to get through them.

NYC aside, most other states I've been to have a 65 mph speed limit plus permit passing within the tunnel. When you've got 55 mph speed limits on the interstates around here, and someone slows down even a little (for whatever reason), all of a sudden traffic is moving below 50 on an interstate. Treat drivers like babies and they're going to act like babies.