From the article I posted: "The key is parallelism, according to Steffen: the ideal scenario is having more than one person sitting down at the same time. "The more parallel you can make the boarding process, the faster it will go,"
With cars getting onto the freeway, this translates to "the ideal scenario is having more than one car get over to the left (fast) lane at the same time".
In practice, many drivers getting on the freeway shoot as fast as possible to the front of the merging lane, which ends, forcing them to cut-off the cars they just passed. This is "linear boarding", the opposite of "parallel boarding". The problem is exacerbated by "one car per green" lights on many freeway onramps, which only make bad drivers want to race down the merging onramp lane even faster to make up for the lost time, typically with the next car doing the same thing. Pretty soon, there's several cars at the end of the merging lane, all needing to get over to the left lane, which they could have merged into and sped away instead of forcing the entire freeway to grind to a halt.
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