In SimCity, there are two different types of road. These are streets and avenues.
Streets are one square wide and avenues are two squares wide. All streets are the same width, so a dirt road can be upgraded to a high density street using the upgrade road tool.
In order to upgrade a street to an avenue, however, you need to destroy the old street and replace it with a larger avenue, which will remove all infrastructure that exists along the old street.
If you're in a situation where you already have the maximum capacity version of a particular style of road but don't have the space to replace it with an avenue, there are other options available. It is possible to build additional roads within the vicinity to alleviate the amount of traffic travelling down your currently over-crowded road. To do this, bring up the traffic data layer to see where all of the traffic is coming from, and build new roads that intersect the busiest streets to provide additional routes for your sims to travel down. The traffic data layer can be accessed using the 'All Data Maps' button in the bottom right of the interface, or by toggling the 'upgrade road' option.
In addition, there is the possibility of setting up mass transit. Mass transit works by building a depot (and adding additional trucks as required to increase the number of sims that can travel per day and reduce the wait time for busses) and placing stops. The region that a stop will cover is highlighted along the roads as you place the stops. For the maximum effect you will want to place stops along your busiest streets (see your data layer for traffic again) and ensure that the wait time for passengers is managed to ensure it doesn't get too high.
You can monitor wait time by bringing up the information screen for your mass transit depot, and you can monitor the amount of traffic a particular stop is attracting by bringing up the information screen for each individual stop.
Commercial buildings (note - single shift versions exist and have half the jobs).
Total § §§ §§§ Tax@10%
§ LD (1x2) 14 10 4 0
§§ LD (2x2) 12 6 4 2
§§§ LD (2x2) 6 3 2 1
§ MD (1x4) 76 60 16 0 §110
§§ MD (4x4) 34 20 10 4
§§§ MD (4x4) 30 10 12 8
§ HD (2x4) 710 600 100 10 §260
§§ HD (4x4) 670 400 200 70
§§§ HD (4x4) 620 200 300 120
Industrial buildings
Total § §§ §§§ Tax@10%
T1 LD (2x4) 26 20 6 0 §80
T1 MD (4x4) 172 140 20 12 §320
T1 HD (8x4) 1620 1400 200 20 §800
T2 LD (2x4) 24 12 8 4 §90
T2 MD (4x4) 132 80 40 12 §370
T2 HD (8x4) 1330 800 400 130 §920
T3 LD (2x4) 22 4 10 8
T3 MD (4x4) 92 20 60 12
T3 HD (8x4) 940 200 600 140
Utilities
Garbage Dump 26 20 6 0
Large Fire Station 172 140 20 12
Police Precinct 76 60 16 0
Recycling Center 132 80 40 12
Water Pumping Station 132 80 40 12
Education
Community College 50 40 10 0
University 460 320 100 40
Metal Working
Smelting Factory 1620 1400 200 20
Trade Depot 26 20 6 0
Trade Port 56 40 12 4
Processor Factory 92 20 60 12
Consumer Electronics 1040 200 600 240
Power Plants
Coal Power Plant 26 20 6 0
Oil Power Plant 56 40 12 4
Reflecting Pool 7 5 2 0
Amphitheater 7 5 2 0
And, because I'm having so much fun bulldozing things... residential building values for workers, shoppers and students:
Workers Shoppers Students Tax@10%
§ LD (1x2) 4 2 2
§ MD (1x4) 40 20 15
§ MD (2x4) 40 20 15
§ HD (4x4) 400 200 100 §200
§§ LD (1x2) 2 1 2
§§ MD (4x4) 20 10 10
§§ HD (4x4) 200 100 50 §240
§§§ LD (4x2) 2 1 1
§§§ MD (4x4) 7 3 4
§§§ HD (4x4) 70 33 30 §280
Additional information
Modules do not have influence.
Best Answer
The vast majority of commercial/industrial buildings want more low-paid grunts than medium-paid staff and high-paid executives. (For example, one building might want 140 low-wealth, 20 mid-wealth, and 12 high-wealth. A list is here; even the buildings that want more mid-wealth workers have pretty high demand for low-wealth as well.) If you want the demand to go away, you need more low-wealth residential areas.