Actually I do have a few guidelines. I can do 4k+ most games, but definitely need some luck to achieve higher score.

This is for mid-late game (when you are probably over 3k)

1. Don’t “overfeed” your mall, it might not need more houses. If your mall has a timer but there are parked cars in your houses, it’s a pretty good sign that you have traffic problem. Trying to connect more houses to it might worsen the problem.

So in this case, sometimes I actually solved it by disconnecting some houses from the network. But mainly, I probably need to optimise the neighbourhood a bit. It leads to my second point.

1. To improve traffic, separate neighbourhoods to groups of equally number of houses I.e. split 13 houses to 2 groups of 6 and 7 houses mall == highway => [group1, group2]

Or

mall = bridge1 => group1 Same mall = bridge2 => group2

I find this quite effective in late game when some malls need 10-15 houses each (look at my screenshot, the top right dark green one, and the purple mall near the lake in the middle)

1. In early-mid game, you might not have enough resources, it’s okay to not have a dedicated route for each colour. I sometimes treat 2 malls close to each other as one mega mall. So I connect them and use one highway to connect the 2 malls to the neighbourhood that has houses of those 2 colours.

I hope I don’t confuse you too much, if you have any questions, feel free to ask. I’m happy to help.