How are straight roads made straight over long distances?

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I can figure a string line, but if you are using a 500 foot string line and you are even off by 1/2, that will end up being in a completely different part of town or on someone’s property by the time you are done. Do they just guesstimate and then when they see they are coming off they make curves or adjustments in the road? I know most roads arn’t straight, but the process still fascinates me.

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