6 remaining buildings are residentials of low, medium and high value and they all fit perfectly. Parks next to it don't fit perfectly as well, but you will get same problem with standard block sizes as well. Unfortunately it's not same with commercial buildings - sometimes two high density buildings will fit the block perfectly, sometimes one high density building will take about 90% available space, not leaving enough room for anything else (look on the selected building below): In such block, every so-called '4x4' residental building will fit perfectly. Measuring in simoleons is the best way I found so far. The ideal block size for an intersection-heavy streets is 1458$ long avenue (low traffic) or 2914$ high density avenue (without streetcars). I may be wrong here, as Sims can't stay on an intersection and an intersection-heavy design decreases movement smoothness, but as I've done some experiments I thought I would share. Since even on a dirty road some services like firemen or moving truck will never turn left (from the road to a building or other object) but will instead go to the nearest intersection (or end of the road), turn back, go back to the building and then turn right to it, in my opinion the ideal road consists of many intersections, thanks to which paths of cars and buses are shorter, and so they spend less time on the road and so they leave the space for other cars sooner. The second gridline will provide enough space for two high density buildings back to back and a gap inbetween that could fit a road (or is potentially useful for narrow parks). Mouse over road with road selected: The first gridline will provide just enough space for a single high density building to exist between the roads. Mouse over road with avenue selected: Same as above Mouse over avenue with avenue selected: Same as above Mouse over avenue with road selected: The first gridline will provide enough room for two high density buildings back to back making for maximum use of the space given the two road types you want to use.

The gridline displayed for a given road depends on what road you moused over and what road type you currently have selected.

Turning on the 'gridlines' feature when plopping a road tile will display gridlines for the last two road tiles you mouse over. Luckily the game itself provides an excellent tool to help you with this. I'm going to assume that most people are interested in the most efficient use of a given space for high density buildings allowing you to stuff as much population/commerce/jobs into your city as possible. To answer this I'm going to need to establish some criteria for 'ideal'.

Simcity 5