The Faulty Algorithm That Plagues American Transportation


What is ‘Travel Demand Models’

Roads and other transportation projects are decided by travel demand models that are designed to determine travel problems of varying sizes and types. They can be designed to address whether or not a small suburban avenue should get revamped or if another lane should be added to a highway. The earliest of these travel demand models were very rudimentary but they’ve gotten a lot more complex nowadays. However, all these models are based on what engineers call a Four-Step process.

American Transportation

The 4-step process

The Four-Step process/algorithm takes in rough estimations of what people consider before traveling and then produces an approximation of how many trips will be taken on certain roads. As its name implies, this algorithm can predict how many trips a route will get through four steps. The first of these steps is that it creates a numerical map using expected travel patterns; one of these is that businesses generally travel more than individuals. In the first step, socio-economics factors like employment levels in a certain area are also considered as places with high employment rates tend to get more traffic. The second step is that the algorithm has to guess where routes generally start and where they end. After this step, the algorithm will then try to determine what means of transportation people might use. Lastly, the process ends with plotting routes for people by determining which one will take the least amount of time to get through. When the process has run, planners and engineers will add a prospective piece of infrastructure to the algorithm and see if it can make a difference. The numbers in the first step can also get changed to be in-line with expected employment or population growth.


4 Step process – Pros and cons

While some experts like Greg Erhardt, who is a civil engineering professor, say Four-Step algorithms are a good way to verify the validity of a certain project, many disagree. Most experts, especially those in the urban planning sector, argue that these algorithms aren’t good at determining a project’s validity. They say this because these models support anyone who assumes that wider roads and more highways reduce traffic. Whether or not these algorithms produce better results is not the only thing that concerns these experts, though, but that we rely on them a lot. Experts are not just arguing against modelling algorithms; they are debating the decision-making process that affects how American cities are designed. What makes experts argue against relying fully on algorithms to plan transportation methods in the future is that they are very rigid. An algorithm can support a company’s idea to build an extra road due to forecasted economic growth or the notion that the population will increase in a certain area. However, these statistics can change and that is why experts believe a human should also have a say in the process to address issues beyond efficacy. These issues are tangible concerns like building cities with quieter streets, accessible public transport, and less need for private vehicles.