Where Should We End The Three Lane Expansion on 141 @ State Bridge?

The City of Johns Creek is suggesting that we widen 141 to three lanes between State Bridge Road and Grove Point Road.  I suggest that is not required.

Forgive me for my crude markings on the photo, but this is all we need to do to drastically improve the functioning of the 141-State Bridge Road Interchange.  The red lines on the map show approximately where I would start the southbound three lanes and end the northbound three lanes.

Reasoning?  There is not a valid reason to expand the road three lanes from Grove Point Road South because the light at State Bridge Road is not green long enough to process all the vehicles that would be between those two points.  But, by making the area south of the red lines below three lanes through(nearly all the asphalt is already present, then the light would be able to process nearly 50% more of the vehicles.

This accomplishes a very important task.  If the light at State Bridge is handling that many more vehicles, the queue backing up on 141 south will be much slower to build during peak periods and dissipate faster as those periods end.  It is possible that the intersection at Grove Point and 141 may not even see many of the issues we have discussed that happen at 141 and Grove Point.

HOW MUCH DIFFERENCE COULD IT MAKE?

The increase  by adding the third lane through southbound on 141 utilizing asphalt we already have in place (close to 50% increase of the vehicles clearing 141 and State Bridge) could very well eliminate the backup we see at the intersection of 141 and Grove Point Road, alleviating the cause of the problem.  It would certainly slow down the creation of that backup queue at the start of rush hour and end it sooner.
Think of it this way:  If the third lane southbound clears an additional 30 vehicles each light cycle, and there are 15 light cycles per hour, then there would be 450 fewer vehicles in the queue at the end of the hour.  I’d estimate that would reduce the length of the backup queue by close to 4/5th’s of a mile.

Here’s the Math:

30 vehicles more 15 times per hour equals 450 vehicles/hour
An average vehicle is just under 17 feet.
Those 450 fewer vehicles would be spread over two lanes so we divide by 2 for a queue of 225 fewer vehicles per lane per hour.
17 feet * 225 vehicles equals 3825 feet or .72 miles.
What is the actual distance between State Bridge and Grove Point Road?  0.41 miles.

What If That Is Not Enough?

If this does not resolve the issues we have at Grove Point and 141, then I’d suggest the implementation of a Fatter intersection leaving St.Ives and Medlock Bridge, with dedicated left turn lights from St Ives.

I’ve also suggested a sensor south of that intersection on 141 so that if indeed the traffic backup reaches beyond the entrance to the high school, traffic on 141 south is stopped.  This would allow right turning traffic from Medlock Bridge to proceed, and then stopping all North and Southbound traffic, allow the St Ives traffic to turn left without having to compete for space from Medlock Bridge(those vehicles are now already down the road.

 

This entry was posted in Johns Creek, Traffic, TSPLOST by EJ Moosa. Bookmark the permalink.

About EJ Moosa

EJ Moosa believes that a smaller government is a more efficient government. He believes that better analysis leads to better solutions. A graduate of Georgia State University In Business Administration, EJ grew up in Cobb County graduating from Osborne High School and worked at several Atlanta companies including First Atlanta, IBM, and Six Flags over Georgia.

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