My main concern is the realism of transportation systems, which many before me here have already pointed out. However, I have more specific grievances:
In SC4, Maxis incorrectly labeled their roads. "Roads", "streets", "avenues" are NOT terms that designate the size, capacity, speed limit, etc. of a given road. Pave any 2-lane city street and you can name it an "avenue," a "road," a "way," whatever you like. These terms they labeled were not accurate and not indicative. Instead, on my "wishlist" I ask that the roads be more accurately labeled. "2-Lane Arterial" "4-Lane Arterial" etc. for in-town roads.
Next, intercity roads. They COMPLETELY got this wrong. A "highway" does NOT mean it's a freeway! What they labeled "highway" and subsequently has everyone on this website referring to as a "highway" is a freeway. If you were to carve out a footpath between two cities, it would be a highway. THAT is a highway. Any form of non-rail ground transport that leaves a city and travels to another locale. The new SC should have a "Highways" panel that would include:
-"2-Lane Highway"(YES, a 2-LANE ROAD can be a highway. I can drive on one to leave the city I live in right now.)
This would have options for Passing Zone, No Passing Zone, Passing on One Side, No Passing on the Other, and turning lanes(making it technically 3 lanes, but it would still be 2 lanes in each direction)
-"3-Lane Highway"-Same Passing, No Passing, etc. options. Also, of course, you'd be able to determine which direction gets 2 lanes and which gets the remaining 1 lane. Also, same turning lane situation applies.
-"4-Lane Highway"-Many options here. Median/No Median. Divided/Undivided. Turning Lanes On/Off.
-"Freeway"-(for those who don't know: a freeway is a limited access road that cannot have at-grade intersections. I.e., one can only enter a freeway on entrance ramps and exit on exit ramps(limited access), and the freeway may not cross another transportation's path, so it must have a bridge over it, or it must go under it(no at-grade intersections). Freeways should have the 4-Lane, 6-Lane, 8-Lane, and 10-Lane options. Then, you can use a tool to drag the entrance and exit ramps out of the freeway, as well as drag flyover ramps out of it to connect with other freeways or even surface streets(this DOES happen in real life). This was another big complaint for me in SC4: You were confined, and still are, even with the NAM, to certain pre-built ramps for freeways. In real life, this never happens; almost every entrance/exit ramps and flyover is unique and specific to that area. Maybe it's very very long and winds far from the freeway to avoid an obstacle. Maybe it's very short. Dragging them in SC5 would allow for road systems that don't force you to bulldoze tons of your development.
And that is all. Just a road system that is functional and realistic. But I'm not going to hold my breath that it's going to happen.