Here’s a chart from a traffic engineering study (out of the University of Nevada*) that simulates the effects of 4-3 road diets on automobile speeds at stop sign controlled intersections.
The upshot of all this is that there are a lot of variables which enter into the picture when studying traffic impacts of 4-lane (Death Road™) vs. three-lane designs. For example: how many buses are there? What percent of the traffic is trying to turn left at two-way stop sign controlled intersections?
(The one thing that doesn’t enter into these LOS simulations, however, is pedestrian and bicycle traffic and/or safety concerns.)
There are a lot of different studies and arguments about the feasibility of 4-3 road diets, and at what point the tradeoff between safety and traffic speeds starts becoming one-sided. This kind of analysis is just one small piece of the puzzle.
*Note: I have no idea how peer-reviewed or thorough this study might be. It seems to have been presented at a convention-type thing in 2011.
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