The road that Ronda did not need
The road that Ronda did not need
It all happened very quickly. An email, a call, and a few weeks of intense study. Submission of the report, three interviews, two meetings, and a very good feeling.
There are jobs that are worth telling and reminiscing about. This is the story of one of them.
It was a morning like any other. A good coffee and a lot of enthusiasm ahead. Sitting in front of the PC, I saw an email that I hadn't opened, which happens when you have two email accounts. That's what crossed my mind—fix this one of these days… While my head was scolding me, my eyes were drawn to that email from an unknown sender that didn’t look like Spam. And indeed, it was a job proposal regarding a Sustainable Urban Mobility Plan that was in the public information period in Ronda (Málaga). It didn’t go into details, so curiosity and business sense made me respond quickly.
A few hours later, I had my first conversation with the Ronda and Comarca 2030 Association. Very kind and concerned people from Ronda who explained the job details to me. I listened carefully, noting that what they were looking for aligned with my values and ideals. So, I decided to accept the task, and without further ado, I got to work.
The job involved studying the SUMP of Ronda and an innovation in its General Urban Development Plan (PGOU), and how one justified the other. In plain words, the SUMP justified a new road that passed through meadows, streams, and rivers, in other words, through a rural area next to the city, with high landscape value, which is also classified as especially protected and has a high sentimental value for several groups in Ronda, as I later found out in the meetings I held.
First argument: A new road is projected as a result of the SUMP
The first idea that crossed my mind was, how does a SUMP justify the creation of a new road? Unheard of. We spent the entire 20th century building roads everywhere, justifying them by the increase in traffic demand. The SUMP should not go in that direction. On the contrary, SUMP were created as a tool to change citizens' habits, ultimately to promote sustainable mobility. I almost had my first argument. It needed to be dressed with technical and scientific evidence, and they existed. Increasing the road network causes the pernicious effect of induced demand. In other words, it facilitates the use of cars to the detriment of other modes. I was saddened because, as professionals, we must not lose the essence of what we are doing. I set myself the goal that it wouldn’t happen to me.
How the SUMP justified the construction of a new road Having finished the first argument, and after carefully reading the SUMP and the innovation of the PGOU of Ronda, I delved into the justification, and it was as follows. Several measures proposed in the SUMP focused on the semi-pedestrianization of the city center. The SUMP modeled the traffic, with various scenarios simulating what would happen with traffic restrictions in the city center. The result was that the ring road traffic increased considerably, going from a supposed current level of service D to E. With these results, the SUMP author suggested a new road to alleviate the ring road, which was modeled in a new scenario, and calculated a new volume and level of service for the ring road, returning it to the supposed level D. The author of the innovation picked up on the SUMP and justified the construction of the new road based on the modeling, scenarios, and conclusions of the SUMP.
Second argument: They used an assignment-only model, without modal distribution
And so, without going deep into the simulation, I found that the model used was assignment-only. This model has certain limitations; one of the most important is that it doesn’t admit modal distribution. It is an easy model to implement as it is based on current trips, from which origin-destination matrices are determined, and finally, the movements are assigned to the road network. And I say road network because here we are only considering car trips. In raw terms, it means that all SUMP measures to promote sustainable mobility (leaving the car to walk or use public transport) have zero impact. This is where I developed my second argument: the SUMP author had not considered any change in the mode of movement in Ronda.
Level of Service as an excuse
Now it was time to delve into how the calculations were made. A bit of reverse engineering was needed, as these documents usually don’t clearly explain where the results come from. Where to start? Sometimes one runs out of ideas. When that happens, you have to go back to the basics, which is not simple, but rather finding what the argument's foundation is. The basic thing here was that the level of service went from D to E. The level of service is a term that measures road congestion. It is the ratio of the volume of vehicles divided by the capacity of the road they pass through. For example, if 90 vehicles/hour pass through a lane, and the lane's capacity is 900 vehicles/hour, the ratio is 10%, and the level of service is A, which is the best. If, on the other hand, 900 cars pass, the ratio would be 100%, and the level of service becomes F, which is the worst. Between these are levels B, C, D, and E. So, it was necessary to focus on how the traffic volume and the ring road capacity were calculated.
Third Argument: Overestimated traffic volume
My third argument was about the traffic volume considered. The demand model used was a daily model, and to calculate the peak hour, the SUMP author had considered 10% of the day concentrated in one hour. So, if there were 12,000 vehicles/day, the peak hour would have 1,200 vehicles/hour. This is a general case; the next question was whether such a case applied to Ronda. To find an answer, I analyzed the data for Ronda from the Ministry of Transport, Mobility, and Urban Agenda (MITMA). MITMA publishes aggregated data per hour for all trips over 500 meters. In Ronda, it was the case that traffic intensity remained quite constant from 8 am to 9 pm, so daily trips are evenly distributed over more than 12 hours. Here, the general case did not apply. The traffic volume in the SUMP was overestimated.
Fourth Argument: The ring road with the same capacity as an urban road
Finally, it remained to analyze the capacity used to calculate the level of service. I realized that the author had used 900 vehicles/hour/lane, which is a correct capacity for urban roads, with intersections and traffic lights. However, the author used this same value for the ring road, which is designed for higher speeds, with grade-separated intersections, designed for duplication, without traffic lights… It couldn’t be. The ring road was considered an urban road! It seemed like a more than significant error. The construction of a new road was being justified because they had considered the same capacity per lane for the entire network modeled, without distinguishing between urban roads and the ring road. For clarity, standard capacity values range from 900 vehicles/hour/lane on urban roads to 2,200 for highways; the ring road should have had between 1,400 to 1,600 vehicles/hour/lane.
I recalculated the level of service, showing a current situation with a level of service B, consistent with what I saw in Ronda during my visit. Under the most adverse pedestrianization scenario, the level of service on the ring road went to level C.
I carried out several auxiliary checks, as I couldn’t believe it. I realized that the road network in Ronda was very resilient and could support the traffic from the pedestrianization of the center and much more.
I feel sorry for the SUMP drafting team, but I feel worse for a rural, landscape, and emotional environment that will lose its nature to become a road, due to a chain of misunderstandings based on significant errors, and a more than significant mistake.
Below you can see the images of the area where the road is intended to be built, the general view of the A-397 bypass, and the preliminary design of the road.
