I'm not sure what you mean about time on site, could you explain? They've been building this section of bridge "on site" by my understanding of the phrase, and have had the road way under the bridge diverted by construction for the past year. It appears to have been permanently redirected now. I assume during some of the work to the existing bridge, they've had traffic slowed, diverted, barreled, etc. Actual moving of old section out and new section into place in three days seems to pretend this was a speedy project with only minor disruption to local traffic, which doesn't seem quite right to me. I guess if the thought is just that that highway connected to the bridge is only (fully) closed for three days, that's certainly worth something over having it closed for the year it took to do the project.