Take the Train or Drive

Each morning, Theodore McGinty wakes up in his tiny bungalow, makes a cup of coffee, and grumbles that he lives in the shadow of the water tower at the edge of town. He walks half a block to the bus station and hops on a bus to work at Honest Carrie’s Used Cars. Meanwhile, downtown, Bella Goth leaves her exquisitely decorated 22nd floor penthouse in the Quigley Apartment Building, rides the elevator to her heated underground parking spot, drives her luxury car three blocks, parks, and greets her first customer of the day at her high-end boutique. At the end of the day, Bella leaves work and picks up groceries on the way home; later in the evening she walks to a restaurant and then to a movie. Theodore and Bella are Sims living in SimCity 4 Deluxe, which models transportation and job choices on a person-by-person basis, closely mimicking software used by traffic engineers, such as CORSIM and Synchro/SimTraffic.

Previous versions of SimCity used images of individual cars, trains, and pedestrians to show traffic congestion and transit usage, but these icons were really just a crude reflection of aggregate transportation usage. Traffic levels were calculated based on the balance between commercial/industrial and residential land use. In real life, each type of residential, commercial, or industrial development generates a different traffic pattern (based on time of day and number of people visiting), so the previous model glossed over the nuances that create traffic problems in real cities. The new game updates the transportation component to include such details. It also actually models the “lives” of individual city-dwellers. A player can now “move” a Sim into a residence in his or her city, see whether that Sim can find a job, whether it stays in its residence, and hear its general perceptions of the city. If a player fails to build enough industrially zoned areas, for instance, an engineer like Gustav Knifefork might complain that he has to commute to the adjacent city to find a job.

The new game engine transforms each city’s transportation grid into an invisible network of paths in which each mode of transportation occupies a different sub-network. With automobiles, for instance, streets are assigned bidirectional paths, one-way streets are assigned unidirectional paths, and medians and other barriers truncate and redirect these paths. Train, subway, and bus stations link the sub-networks, providing connections among possible foot, automobile, and train paths. Once created, the network generates multiple layers of traffic simulation: commutes from home to work, freight movement from industrial areas to SimNation, and other trips to commercial areas and tourist attractions.

To calculate the number of trips that the transportation network must handle, the traffic model relies on a concept called trip generation, which, though not perfectly accurate, is generally accepted as the best currently available means of transportation planning in the real world. Each building generates a certain number of trips. For example, an office building with 100 workers generates 200 trips per day (100 arrivals and 100 departures). When a player zooms into an area with a high concentration of office buildings, she will see a steady stream of traffic heading towards the zone in the morning and away from the zone in the afternoon. A road that handles midday traffic with ease may become gridlocked at rush hour.

Two factors dictate the mode of transportation that each trip uses: the travel time from origin to destination and random preferences based on income level. The game uses an algorithm which assumes that lower-class Sims like Theodore McGinty are more likely to take the bus while middle-class Sims like Gustav Knifefork prefer trains and subways, and upper-class Sims like Bella Goth are most likely to drive their cars. Upper-class Sims will take the bus only if the bus decreases travel time enough to outweigh their propensity to drive their cars.

As in real life, when traffic congestion reaches critical levels, the Sims will demand solutions. Built into the game are a series of characters that act as the city’s advisors. The transportation advisor, Jamil Herd, makes general suggestions about improving road capacity and providing options for mass transportation. Herd’s solutions are akin to basic solutions used in real cities. When traffic congestion and residential density increase to a certain level, Jamil suggests building bus stations, and as the city’s size increases further, Jamil suggests adding trains and monorails. When commutes get too long, Jamil may suggest moving jobs closer to residential areas.

Real traffic simulation software is complex enough to require specific training and powerful computers. Many details in the real-world models are appropriately left out in the game to avoid overwhelming complexity–users do not have to worry about signal timing or right-turn lanes, for example.

But the game should do a better job at including cutting-edge solutions like High Occupancy Toll lanes, specific truck routes, and long-distance bike trails. If SimCity really has an educational mission–and one cannot help but think that some players who regularly sit in stop-and-go traffic on their way to work might consider how the game’s suggestions apply to their towns–it could play a critical role in disseminating information to the public. Passionate civic advocates are usually the driving force behind getting transportation improvements built, but their knowledge of new possibilities often lags years, even decades, behind that of transportation professionals. Perhaps SimCity 5 could incorporate these innovative strategies and help build a cadre of smarter transportation advocates in communities across the nation.