How many empty car seats should we harness through ridesahring, to end up traffic jams and air pollution?

We have a problem in the city: traffic jams cause 80% additional pollution and increase travel times three to four times. This happens because too many cars that carry nothing but the driver and several empty seats, collapse the traffic routes. If we share some of these empty seats (carrying people who go in our direction) we can easily get rid of these problems.

We currently use our cars quite inefficiently. The vast majority of them carry only one person (the driver), and waste four empty seats. We can say that, every five cars that circulate by a city as Madrid, four of them carry just the driver, and the fifth one carries only two people.

Thus, we use many more cars than necessary, squander an increasingly scarce fuel and we are polluting excessively the air we breathe. It is not really the smartest way to get around, because we are throwing away money and creating health, traffic and parking problems for ourselves.

Everything gets complicated by the daily evolution of traffic.

We citizens are subject to certain schedules and the demand for transportation seats varies greatly throughout the day. There are two very marked demand peaks, at the morning and afternoon peak times, when going and returning to work, as can be seen in the green line of the graph.

However, the maximum number of vehicles admitted by streets and roads is constant (blue line of the graph), and something similar happens to the number of seats available on public transport.

1-transport-offer-and-demand-by-the-hour

Unable to handle these peaks of demand, the usual traffic jams happen at rush hour, when the available transport means doesn’t seem to be sufficient.

However, this is not entirely true.

As a million cars circulate in Madrid every day, it means that we are wasting four million valuable empty seats (there are more empty seats that people travelling by metro and bus). And besides, most of these seats are vacant at peak times, just when they are needed most and when we suffer most transportation problems.

Could we take advantage of our empty seats to have fewer problems and live better?

Lets study in detail why traffic jams occur, and their pernicious effects:

In the following graph, the black line represents how the number of vehicles that circulates over time (the actual traffic) evolves. On the left side we have a growing but fluid traffic, which is able to satisfy the demand, because the cars can travel without problems. Problems start when the maximum capacity of the road is reached. This usually happens in Madrid’s M-30 about 7:00 in the morning.

When the number of vehicles entering the roadway exceeds its maximum capacity, it becomes saturated. The cars start braking and, suddenly, the capacity of the road to admit vehicles is drastically reduced.

2-peak-time-traffic-evolution

From that moment on, despite the fact that demand continues to rise, the number of cars circulating actually drops. We pass into a congested traffic situation, where the black line showing the real traffic decreases and drifts apart from the demand curve (the discontinuous blue line, which continues to grow); So that more and more of the demand is dissatisfied. Cars have to wait to be able to enter the main routes, or they have to take a detour looking for an alternative road.

The most notable and damaging effects of traffic jams are:

  •  A sharp decrease in speed (eg. in Madrid’s M-30 the speed drops from 55 to 15 MPH), which makes travel times three to four times longer.

3-speed-evolution-at-peak-hour

  • Each car caught in the jam pollutes an 80% more (According to a study of M .Treiber from the University of Dresden)

4-pollution-evolution-at-peak-hour

Once we have a congested traffic, the situation seems insurmountable, since there is too much difference between the number of cars that want to circulate and those who really get it.

The only solution is to anticipate, removing from the traffic a sufficient number of vehicles as to avoid that the roads become saturated.

For this purpose, we can take advantage of the empty seats in our cars.

Imagine that we managed to convince a certain number of people to offer the empty seats in their cars to carry some passengers, while they are on their way to their daily occupations. Therefore, each of them will remove from the traffic several vehicles (from one to four, according to the number of passengers they carry), since each of those now going as passengers, no longer need to move their own car.

This behaviour change, which efficiently takes advantage of the sharing of the empty seats of some cars (instead of going in each one’s own car), causes two benefits in traffic:

  • All the people who need it can be easily carried, in a smaller number of vehicles (without getting to saturate the road).

5-people-vs-cars

  • Compared with the situation we had when the traffic was congested, the effective capacity of the streets to transport people increases (according to the green area of the following graph)

6-extra-capacity-by-ridesharing

It also has two effects on pollution improvement:

  • First of all, the passengers’s cars no longer pollute, since they remain parked.
  • In addition, by removing these cars from traffic, routes do not become saturated, and we prevent traffic jams.
    This practically doubles the effectiveness of the fight against pollution; Because all cars are in a fluid traffic, and will no longer pollute that additional 80% that they emitted when they were in congested traffic.

How many rides do we have to share to avoid the traffic jam?

To keep a road decongested, we just have to remove the excess cars that cause the jam (the number of cars between the saturation level of the road and the peak of the demand).

To achieve this, it would suffice to share a relatively low number of rides. The fact that each carpool can offer up to four passenger seats, is a multiplier effect that works in our favour.

In the worst case (if each car shares only one passenger, and still keeps three empty seats), it would be necessary to share as many cars as the surplus demand over the capacity of the road.

However, in the best case (when each car completes all its empty seats and carries four passengers) the situation is as shown in the following graph, and it suffices to share a number of cars four times lower.

7-cars-for-ridesharing

Although the rest of the vehicles continue going the same as before (only with their driver); both these and the shared cars will enjoy a fluid traffic, with the advantages for everyone of a great reduction in pollution and travel times.

To sum up:

Traffic jams in the city, cause 80% more pollution and three or four times longer travel times. We can easily avoid them, by simply sharing the empty seats of some of our cars, to carry as passengers other people going in our direction.

DedoCar is a smartphone application that finds an empty seat in a car that can carry you; Or if you decide to share the empty seats in your car, it locates on the fly the passengers that you can carry while you are on the way to your destination point.

If you want to save time and money, and solve your city’s problems, join the community of ridesharing committed travellers at dedocar.com !

 

Note:
This article has also been published by Move Forward (Daimler group): https://www.move-forward.com/how-many-cars-do-we-need-for-carsharing-to-eliminate-traffic-jams/

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