If cars were made with just enough hardware to reach or slightly exceed the national speed limit, won't it be cheaper to produce and more affordable?

What is the point of producing a car that is capable of reaching 200m/h where you shouldn't exceed 70m/h.

There is a coming law that will require car manufacturers to add a traffic sign reader to cars where it limits the speed of the car to the limit where it is.

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    $\begingroup$ This is an automotive engineering question, not an economics question. In any event, if a car can barely reach 60 miles an hour on a level surface, I think it would have difficulties driving on steep grades. $\endgroup$ – Brian Romanchuk Feb 18 at 19:32
  • $\begingroup$ But I am not asking about the technical side of this, my question is about the cost and profit, the business model around making the car with this spec. I think car's ability to claim steep grades is due to its bhp not highest speed, which are not the same. $\endgroup$ – Mocas Feb 19 at 13:34
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    $\begingroup$ My background is in electrical engineering, but it is very safe to say that this is almost entirely an engineering question, and partly a question of marketing. There is no reason to believe that your discussed option is technically feasible or whether anyone would buy such an underpowered vehicle (how does it carry loads?) so there is no point in discussing the economic theory. It is very much akin to asking about the economics of perpetual motion machines. $\endgroup$ – Brian Romanchuk Feb 19 at 14:23
  • $\begingroup$ Many online articles describe China as the producer of the most affordable vehicles. You could compare the performance specifications and design of these cars to the vehicles in Europe, United States, etc. In general the United States subsidizes low cost gas and has larger more powerful vehicles compared to places where gas is expensive. Cars must be lower weight, reduce rotational inertia in the driveline, and more aerodynamic to be more fuel efficient for given motor characteristics (torque x angular speed = horsepower). Smaller lighter cars tend to be more fuel efficient and lower cost. $\endgroup$ – SystemTheory Feb 19 at 15:07
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    $\begingroup$ I’m voting to close this question because it does not belong on economics stack exchange $\endgroup$ – csilvia Feb 23 at 13:46

As well as the other answer, I would add two further points.

Firstly, smaller engines with lighter components tend to entail faster moving parts internally, or higher fuelling loads which exert larger forces over smaller component areas, and so must generally work "harder". This not only impairs the long-term reliability and durability of the engine, but in some cases, requires the engine to be driven much faster and in lower gears in order to achieve the desired acceleration or power output.

The other point is that the necessary power output is determined not just by engine design or driver choice, but by driving norms and the standards of road engineering, and therefore an inadequately-sized engine may spend most of its time being driven at high revs and low gears, well outside optimal parameters even for fuel consumption, let alone optimal parameters for reliability.

I noticed this once when given an underpowered hire car. It was so underpowered that it routinely had to be driven to the redline, with the accelerator constantly to the floor. The effect was that fuel consumption soared beyond normal levels, for a responsiveness that was ultimately still inadequate.

Other drivers will also retribute attempts by drivers to penny-pinch on fuel by driving small-engined cars inconsiderately and unresponsively, by driving aggressively, by overtaking, and by otherwise causing the mental (or accident risk) burdens on the tardy driver to increase.

  • $\begingroup$ I am not an automotive engineer, nor do I have much interest in cars, but this appears to be the correct answer. However, this reinforces the point I made: this is an engineering question, not economics. It would require an audience of automotive engineers to get an authoritative answer, and there is no evidence that this stackexchange page has such an audience. $\endgroup$ – Brian Romanchuk Feb 23 at 13:22
  • $\begingroup$ @BrianRomanchuk, thank you for the praise. I would suggest this is a case of applied economics, since the balance between fuel cost, maintenance costs, and capital costs, are in large part an economic question. $\endgroup$ – Steve Feb 23 at 13:28
  • $\begingroup$ It’s engineering economics. The issue for this website is that the set of feasible options is entirely engineering, and the question is asking whether an option is feasible. The concern is whether any answer given properly describes the engineering issues. A readership of a small number of economists (and others) are unlikely to be able to judge the quality of answers. $\endgroup$ – Brian Romanchuk Feb 23 at 13:52
  • $\begingroup$ @BrianRomanchuk, ah well hopefully such an audience will eventually develop as such questions and answers are put! $\endgroup$ – Steve Feb 23 at 17:48
  • $\begingroup$ Basic physics is enough to discuss fuel economy and road performance. I gave a common sense answer based on personal experience in an effort to avoid discussing the physics, engineering (manufacturing), and economic trade-offs. In terms of physics the engine (source) makes power as torque times angular shaft velocity. Steve discusses internal engine friction. Gearbox is a mechanical transformer that reflects dynamic loads in driveline and chassis back to power source. Loads that call for more fuel/power are acceleration, hill climb, friction, air resistance. Braking converts energy into heat. $\endgroup$ – SystemTheory Feb 23 at 18:28

If cars were made with just enough hardware to reach or slightly exceed the national speed limit, won't it be cheaper to produce and more affordable?

The short answer is yes. However cheaper materials may not provide as much safety in a crash and reduced power in the cheaper engines would reduce uphill driving performance.

I owned a Nissan 5-speed manual pickup truck in the late 1980s. This light duty 4 cylinder truck had lower cost and more fuel economy than other vehicles at the time. I would short shift the transmission, drive the speed limit, accelerate and brake conservatively, all to optimize fuel economy. The fuel economy was often right around 36 miles per gallon highway with the 55 mile per hour speed limit. I think it was about 28 miles per gallon for all local driving at an average speed of about 30-40 miles per hour.

Even though you get more fuel economy at lower speeds the fuel economy for local driving is reduced by stop and go cycles. The brakes dissipate thermal energy to the surroundings as waste heat every time the vehicle is brought to a stop. The fuel burn increases to increase kinetic energy of the vehicle every time the vehicle accelerates. The fuel burn increases to oppose a headwind or climb a hill even at constant speed. So if one desires to accelerate uphill against a headwind then the engine must make reserve power. I often had to downshift my little truck on steep hills, and reduce my speed, when driving uphill or into a headwind, much like the large 18 wheeler trucks would do on very steep grades.

I drove this truck through the eye of the storm during Hurricane Bob. First the tailwinds pushed the truck over 70 mile per hour, then I drove through the calm eye of the storm, and then I had to put the gas pedal to the floor only to drive about 45 miles per hour against the headwinds.

Also driving the steep grades would require reduced speed, below the 55 mph limit at the time, on one long hill I would start by going 70 mph at the bottom and be doing about 30 mph at the top even with no tailwind or headwind.


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