Not to mention people tend to get a little bit cranky about heavy trucks running up and down what are often residential roads too much at night.
One place I was working had this big plan for moving deliveries to night time with one depot on a 5am slot (which was causing considerable issues staff wise as most of them were on day contracts) and had completely overlooked the fact that depot was adjacent to and only accessible through a housing estate where time of day limitations were in force for heavy goods vehicles.
Ended up costing them a considerable amount as the plan was 90% in place before anyone realised and by that time they'd lost a lot of good staff (who'd have gone anyhow if they'd been forced to nights).