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Traffic and transportation specifics #1062
Updated: 10/29/02 OS/platforms(s): All Versions: All

Contributor/author(s): Kyle D.J.

General

SimCity 3000 traffic statistics are based on the concept of "trips". Trips are attempted between points in the city, and the ease with which these trips can be accomplished determines the traffic density on the various routes.

I do not have all of the information to explain exactly how the trips are computed. Instead I will present the information that I do know as it still provides a good, if not complete, insight into traffic.

Travel methods

Travelling takes time, effort, and patience, and each type of transportation method has different amounts of such "costs". This cost is affected by the method of transportation used, and by the traffic density (congestion level). The equation used for every tile is:

tile cost = method cost + density / method divisor

The "method cost" is the basically how slow that method is, so lower values are better. The "method divisor" determines how much that method is affected by traffic congestion, so the greater the divisor the better.

The method costs and divisors are:

Cost   Divisor  Method
~~~~   ~~~~~~~  ~~~~~~
4      25       road
3      30       road by bus
2      100      highway
1      120      highway by bus
8      10       bus stop
6      10       rail station
6      10       subway/rail station
6      10       subway station
2      255      rail
1      255      subway
32     --       damaged tile (presumably the tile type sets the divisor)

So for example, consider a trip from a residential zone to shopping in a commercial zone, and assume the traffic density is 128 everywhere along the route. The total trip cost adds up like this:

 3 X ( 4 + 128 / 25 ) = 27  Walk 3 road tiles from house to bus stop.
 1 X ( 8 + 128 / 10 ) = 20  Waiting at bus stop.
 6 X ( 3 + 128 / 30 ) = 44  Bus drives 6 road tiles.
30 X ( 1 + 128 / 120) = 62  Bus drives 30 highway tiles.
 5 X ( 3 + 128 / 30 ) = 36  Bus drives 5 more road tiles.
 1 X (32 + 128 / 30 ) = 36  Bus drives over 1 damaged road tile.
 2 X ( 3 + 128 / 30 ) = 14  Bus drives 2 more road tiles.
                         0  Getting off bus at commercial building 
                            (buses can stop anywhere).
                       ---
                       239  Total trip "cost".

Of course the example is more complicated if the traffic density isn't the same along the entire route as was assumed here.

Having presented all of this, I have no idea how these trip costs are used in the simulation. Sorry. Presumably they are used to determine if a zone has poor transportation to other zones.

Traffic density

Whenever a trip passes over a given tile (road, rail, etc.) the traffic density for that tile increases by 3.

The maximum traffic density that can exist for a given tile is 255.

Every month traffic for each tile is reduced to 75% of the previous month's value. (Presumably this is to prevent traffic overflow errors?)

Sims travel based on the "herding mentality", travelling on the route with the most traffic. (This could explain why highways often appear so lightly used while nearby streets are congested.) However once the traffic density exceeds 165, they will become annoyed and try to seek an alternate route.

Ordinance effects on traffic:

-10%  roads & highways     Alternate Day Driving
- 5%  roads & highways     Car Pooling
- 2%  roads                    Parking Fines
+ 2%  roads                    Crossing Guards
+ 5%  roads & rail         Tourist Promotion

Zone access

The maximum number of tiles that buildings can be from a road:

4/5  Residential
3/4  Commercial
5/6  Industrial
5/6  Default (all others)
(The second number is if Shuttle Service ordinance is enacted.)

Trip generation

Again, I am not clear on how this works. But here's what I do know...

There is a 20% chance of a trip being generated. (Presumably this is per potential origin per simulation cycle.)

Once a trip has been generated, the chance that it will contribute to traffic density is at least 30%, and increases as population density increases. (No, I don't understand it either.)

Each trip has an origin and destination:

Trips From           Go To
~~~~~~~~~~           ~~~~~
Residential zones    10% to Res.

Commercial zones     70% to Res.
                     10% to Com.
                     20% to Ind.

Industrial zones     50% to Res.
                     20% to Com.
                     30% to Ind.

Other zones/buildings  33% to Res.
Note: The percentage of trips from "Res" and "Other" that go to Com and Ind are based on the ratio of Com and Ind zones existing in the city. So the trip patterns change as the city evolves.

Also note that trips only end at Res, Com, or Ind zones. They will never end at Other zones/buildings, although they can start there.

The chance that mass transit will be used for a trip is 60%, or 80% if Subsidized Mass Transit is enacted. Both of these values assume funding is 100%. Lower funding means a lesser chance of using mass transit; higher funding means a greater chance.

Funding

At 100% funding, the per-tile costs (in simoleans) are:

0.3   highway
0.2   subway
0.02  road
0.01  rail

When funding is below 100%, the percent of road tiles that will become damaged each month is:

( 100 - funding ) X 0.1

Thus if funding is zero, then 10% of road tiles will become damaged each month.

When funding is above 100%, damaged road tiles can become repaired, but at a much slower rate than they became damaged.

There is a chance of a transportation labour strike if the funding is below 70%. The chance of strike is 0% at 70% funding and increases linearly to 35% at 0% funding.

A strike will last no more than 24 months (if the player does nothing).

Income

Mass transit income (per trip, per tile, in simoleans):

0.01   rail
0.01   subway
0.005  bus

Enacting Subsidized Mass Transit decreases transit fare income by 35%.

See also
Pollution specifics
The where and what of mass transit
Transportation infrastructure
Control your transportation flow
Building the perfect mass transit system

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