Having buses run on a designated lane for trains is a much better and superior option.
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However, in this the 21st century a much better option than 19th century street level rail and 20th century bus rapid transit running on a designated lane exists.
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What is this 21st century option?
(1) modern technology to bundle all downtown Honolulu traffic lights into a single system controlled by artificial intelligence -  to manage traffic flow.
A perfect example is how the New Jersey DOT addressed traffic congestion in Meadowlands.
(2) Remodel all intersections in downtown Honolulu with heavy traffic volume into a new intersection design that enables vehicles to make a left turn at an intersection without stopping traffic.  Such as in Utah, Missouri, and Maryland
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A good example of what option (2) can make is that of traffic on Fort Weaver Road where smooth flow of traffic by synchronized lights is interrupted by stopping traffic to allow cars to make a left turn.