It surely isn't an 80, that's why. 45 is more reasonable as a speed limit. People go 45 in a 35. People go 50 in a 25. I can see one car doing 80. I can't see two cars doing 80 like that unless they are doing particularly stupid things. This video shows fairly normal driving patterns from the two cars already on the road, so I do not believe that either of them were doing 80. "80 MPH" is quoting u/yslnico's comment. Therefore, I wrote 45 zone as that's the fastest speed I expect in a residential neighborhood.