Highways at 150 km/h, it takes 4 minutes less but consumption, pollution and safety worsen – Corriere.it

The Minister of Infrastructure and Transport, Matteo Salvini, announced it a few weeks ago: it is the government’s intention, as part of the preparation of the new Highway Code, to increase the speed limit on some motorway sections from 130 to 150 km/h h. But do the benefits really outweigh the negative impacts? Altroconsumo thought about trying to give an answer and analyzed the possible consequences in terms of fuel consumption, pollution and road safety.

20% more fuel consumption (and higher costs)

To go at a higher speed, the engine needs more power to resist the impact with the air and, therefore, this implies an increase in consumption. Altroconsumo explains that, above 120 km/h, a 10 km/h speed increase corresponds to about 10% more fuel (an indicative value, which can vary according to the characteristics of the car). Therefore, going from 130 to 150 km/h for the consumer is equal to +20% of petrol or diesel. One of the stretches where the speed limit on the A4 between Milan (Milan East barrier) and Brescia West is expected to be increased (one of the stretches where it seems possible that the limit will be increased to 150 km/h), route about 75 km long. For example, a car that at 130 km/h consumes 8 liters every 100 kilometers will consume around 6 liters on that route. Taking into account the current average price of petrol, which according to Staffetta Quotidiana is around 1.80 euros per litre, the cost is 10.80 euros. At a speed of 150 km/h, the consumption of the same vehicle every 100 kilometers rises to 9.7 litres, equal to 7.3 liters on the 75 km stretch and, therefore, at a cost of 13.10 euros (with a cost in excess of 2.30 euros).

The impact on the environment

Higher fuel consumption increases the level of pollution, being directly proportional to CO2 emissions. So whether to travel at 150 km/h instead of 130 km/h requires 20% more petrol or diesel, also emits 20% more CO2. This is not the only element harmful to the environment to be released in this context, particulate matter and nitrogen oxides (NOx) are also emitted with the fuel consumption of cars but the ratio is not proportional and is therefore more difficult to calculate their impact.

Road safety: more stopping space

The risk also increases in terms of road safety. Indeed, according to Altroconsumo estimates, an increase in the speed limit of 20 km/h will require 43 meters more of stopping space between one vehicle and another. A figure that is obtained from the difference between reaction space and braking distance: the first is the one that elapses between the moment in which the driver perceives a danger and the one in which he presses the brake pedal, which at 150 km/h becomes 42 metres compared to the 36 necessary with a speed of 130 km/h; the second, on the other hand, is the one that takes the car to stop completely once the brake is activated and depends on many factors (mass of the car, effectiveness of the braking system, etc…) that are difficult to calculate but also on the speed used. According to calculations by the consumer organisation, the stopping distance at 130 km/h is 149 metres, while at 150 km/h it would be 192. Furthermore, as speed increases, so does the possibility for the car skidding or loss of control in the event of a quick and sharp input on the steering wheel.

More serious accidents against reduced journey times

If a motorway accident occurs at a speed of 150 km/h, it potentially also entails more serious damage to both the cars and the people involved. The kinetic energy of a moving body is proportional, in addition to its mass, to the square of its speed: hence the mathematical formula E= (mv²)/2, i.e. mass times speed squared divided by two. Assuming that the mass of the vehicle is 1,500 kg, if it travels at 130 km/h its kinetic energy will be 980 kJ, while if it travels at 150 km/h it will increase to 1,300 kJ. The difference of For example, 300,000 joules is the energy required to lift a 30-ton object by one meter. The only benefit consists in the reduction of journey times, also calculated by Altroconsumo: taking as an example the section of the A4 between Milan and Brescia, traveling at 130 km/h and 75 km would be covered in about 34 minutes and 30 seconds; at 150 km/h, on the other hand, it would take about 30 minutes, a saving of only 4 and a half minutes.