Option Lanes that are not Split-Phased

[codyg1985]

After seeing this thread, I thought about the instances I have run across where there is an left turn/straight-option lane governed by a signal that is not split-phased. I came across this situation in Chattanooga at the intersection of Mccallie Ave and Central Ave. Here are overhead signs showing the lane configuration, and here is the signal. I was wishing to turn left at this intersection when the green arrow and red ball were displayed, but I couldn't because someone in that lane was going straight and couldn't. I don't know why this couldn't be split-phased.

[Brian556]

I noticed this as well...very dysfunctional setup.

Also, in this area, there are two RR crossings that have had their lights removed even though the tracks are still in use. I'm guessing this was done to avoid modifying the signals when the streets became two way. Never seen anything like that anywhere else in my life. It's like they don't know what they're doing in Tenn. They have an intersection on US 72 in S Pittsburg that is now signalized, but they left up the STOP signs for the side street.

[Revive 755]

After seeing this thread, I thought about the instances I have run across where there is an left turn/straight-option lane governed by a signal that is not split-phased. I came across this situation in Chattanooga at the intersection of Mccallie Ave and Central Ave. Here are overhead signs showing the lane configuration, and here is the signal. I was wishing to turn left at this intersection when the green arrow and red ball were displayed, but I couldn't because someone in that lane was going straight and couldn't. I don't know why this couldn't be split-phased.

Might be better to either diet Central there and install a TWLTL for a few blocks or install flashing yellow arrows and run it lead-lag.


There are a few locations in Chicagoland where non-split phased option lanes occur, but if it is not a T-intersection, only one direction will be provided with a left turn arrow.

* IL 132 at Granada Boulevard
https://www.google.com/maps?ll=42.410485,-88.034035&spn=0.001685,0.004128&t=h&z=19

* IL 132 at Sand Lake Road
https://www.google.com/maps?ll=42.407833,-88.02966&spn=0.001685,0.004128&t=h&z=19

Both of these will supposedly get dedicated left turn lanes in the coming years.

* IL 43 at 26th Street:
https://www.google.com/maps?ll=41.843166,-87.803416&spn=0.0017,0.004128&t=h&z=19

There's probably more out there I'm not remembering tonight.

[Brandon]

After seeing this thread, I thought about the instances I have run across where there is an left turn/straight-option lane governed by a signal that is not split-phased. I came across this situation in Chattanooga at the intersection of Mccallie Ave and Central Ave. Here are overhead signs showing the lane configuration, and here is the signal. I was wishing to turn left at this intersection when the green arrow and red ball were displayed, but I couldn't because someone in that lane was going straight and couldn't. I don't know why this couldn't be split-phased.

Might be better to either diet Central there and install a TWLTL for a few blocks or install flashing yellow arrows and run it lead-lag.


There are a few locations in Chicagoland where non-split phased option lanes occur, but if it is not a T-intersection, only one direction will be provided with a left turn arrow.

* IL 132 at Granada Boulevard
https://www.google.com/maps?ll=42.410485,-88.034035&spn=0.001685,0.004128&t=h&z=19

* IL 132 at Sand Lake Road
https://www.google.com/maps?ll=42.407833,-88.02966&spn=0.001685,0.004128&t=h&z=19

Both of these will supposedly get dedicated left turn lanes in the coming years.

* IL 43 at 26th Street:
https://www.google.com/maps?ll=41.843166,-87.803416&spn=0.0017,0.004128&t=h&z=19

There's probably more out there I'm not remembering tonight.

Far more than that out there.  Almost every intersection around the area that has two lanes that continue through the intersection and are only controlled by a three-phase signal (r-y-g) are like this.  There's far too many to count!

[Alps]

Yeah, probably best to limit this thread to: "WTF, there's a green arrow for a shared lane?"

[mrsman]

The intersection of Wilshire and Santa Monica in Beverly Hills, is an interesting example:

https://maps.google.com/maps?q=santa+monica+and+wilshire+beverly+hills&hl=en&ll=34.067023,-118.411074&spn=0.012425,0.026157&sll=40.772618,-73.956174&sspn=0.000714,0.001635&t=h&hnear=N+Santa+Monica+Blvd+%26+Wilshire+Blvd,+Beverly+Hills,+Los+Angeles,+California&z=16&layer=c&cbll=34.067018,-118.410949&panoid=OGggJqy0cN3NnAdmQs2ysw&cbp=12,86.53,,0,9.6

If you are on eastbound Wilshire, the left lane turns left.  The second lane is either left or straight.  (Don't let the weird sign confuse use, the pavement markings show an option lane.  In my experience, the vast majority turns left from the option lane.  Almost everybody else makes the next left at "Little" Santa Monica)  The right two lanes go straight.

Here is the signal phase order:

1)Westbound straight and protected left.
2)Westbound and eastbound.
3)Eastbound straight and protected left.
4)Santa Monica Blvd cross-traffic.

Essentially, the Wilshire light is on a lead-lag phase.  The lead-lag is like split-phasing except that there is an intervening period where both eastbound and westbound are simultaneous.  With this specific intersection, the second phase is very short, so for all intents and purposes it does operate as a split-phase, with a very slight overlap.

The next intersection to the east is with "Little" Santa Monica.  There, the left lane is an option lane, the other 2 are straight only.  This intersection keeps the exact same timing as the first intersection, except that the third phase is a permissive left.