Probably the best way to do it is to have the speed limit set per lane rather than for the entire highway. So maybe the speed limit in the right lane is 55, 65 in the next, 75 in the next, and 85 in the far left, or maybe even no speed limit in the far left. And to help make it less complicated, you could color code the lines to correspond to the speed limit in that lane, instead of just having white and yellow lane line colors, like green for 55, blue for 65, etc. etc. Maybe it's too complicated, but it would make it a lot easier to drive.
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