Consuming More Energy in the Pursuit of Saving Energy

Next week, we’ll be putting out a Freakonomics Radio podcast called “The Cobra Effect.” Without spilling the details now, I’ll tell you that it’s about unintended consequences, the kind of stuff that happens when clever-seeming incentives are let loose on an even cleverer public.

With that in mind, I was intrigued by the following e-mail from a reader named Eugene Kim:

My locality in Virginia has mandated biennial emissions inspections for automobiles before registrations can be renewed on those years. Since mine is expiring at the end of this month and it’s been two years since my last emissions test, I took my car to the service station this morning. They don’t seem to actually measure any emissions; they merely check the OBD computer for stored readings.

Here’s where it gets stupid. I don’t drive a lot. I take the train to work so I only drive on weekends, if that. (If you’re wondering why I even have a car, I bought it when I lived in the Midwest and needed it, but moved to the East Coast shortly thereafter and was upside-down on my loan. Plus I feel strangely vulnerable without a car.) Anyway, my car is idle a lot while the battery charge depletes slowly. And apparently, if it drops to a certain point the computer loses all those readings. I didn’t think it had gotten that low since the car hasn’t had any problems starting.

Accordingly, the guy at the service station tells me that my computer is not ready to return any results, and what I need to do is drive around for 150(!) miles so the computer can collect enough readings. So by driving around aimlessly, I’m wasting money, wasting gas, and polluting the environment more so I can comply with this law. My 2005 model car has 9,200 miles on it. Even if it’s the worst-polluting car in the world, how much damage am I doing with that little driving? There’s got to be a better way to penalize emissions, right?

First of all: any suggestions for how this emissions program can be improved?

Second: it would be churlish to suggest that a few stories here and there about the unintended consequences of right-minded legislation invalidate the idea of trying to better our world. But these recurring stories do suggest that when you pursue a goal, no matter how right-minded it may be, with the zeal of an advocate rather than the pragmatism of a skeptic, it’s easy to misfire.

Nathan Denison

The issue is the OBD II electronics used from emissions diagnostics on all post-MY1996 vehicles. OBD doesn't actually measure actual emissions but checks for failure in emissions equipment, and if no failures are found assumes that emissions are fine. (OBD is easily defeated, by the way).

I would be curious is the emissions testing site did not have a tailpipe sniffer (measures actual emissions at the tail pipe, used on all pre-MY1996 vehicles), and if so if it would be an option is this instance.


Engine controllers actually do measure the car's emissions (albeit indirectly -much of it is calculated) - it's inherently neccesary to control the emissions system. Think about it - the ECM needs to know what position to command the EGR valve to, for example. Diagnostics of the health of the emissions system is only part of it. You're correct that it's easilly defeated on many vehicles, though tamper-detection/anti-tamper methods are making inroads (what, you thought they weren't wise to it? :).

Philo Pharynx

While this is a negative unintended consequence, I think we need to examine this in terms of orders of magnitude. How many drivers are in this situation? At 150 miles worth of emissions per user, how bad is this? Compare this to the amount of emissions eliminated from drivers who have cars that don't pass. I suspect the latter far outweighs the former.

Of course in a perfect world there would be a backup for the computer battery.


He could also just get a battery charger rather than use his alternator to charge it (driving 150 miles).


That probably won't work. It seems much more likely that what he's experiencing are "Not Ready" codes from some of the OBDII sensors. That is, for the catalytic converter status to be tested, the car has to be driven long enough for the converter to reach operating temperature. There's a better explanation here:

The other point of OBDII that a lot of people seem to miss is that it gives continuous testing (if the car is driven normally). Instead of an emissions control failure (or other engine problem) only being caught at an annual inspection, it is detected when it happens, and the system turns on the "Check Engine" idiot light. (For non-idiots, we can use an inexpensive scanner to monitor codes and figure out what the problem is.) So it gives built in, real-time monitoring, at little incremental cost because the sensors monitored are pretty much the same ones being used to control the engine.



There's at least one better way to detect emissions problems -- remote testing of cars driving through moveable pollution sensors on public roads. Remote testing readily detects the gross polluters doing the most environmental damage. It is also more likely to catch the cars driven the most and therefore doing more damage. A well run program could probably lower pollution monitoring costs over periodic inspections that require fixed stations, numerous employees and can test few cars per day. A remote sensing program might receive comparable results. It would also be tougher to cheat. Some car enthusiasts mayinstall performance parts that increase emissions for regular driving, but re-install the stock parts just to take the test. These people would be caught under a remote sensing system.

Mark F

This is such an edge case that it is a waste of time to worry about this person's problem. Just drive the 150 miles and be done with it.

Eric M. Jones

Car batteries, even if you don't use them, last about 7 years. A new one might fix this problem. At any rate, you'll need a new one anyway.


Remote sensing of cars in traffic for pollution violations is probably much more efficient (new or compliant cars don't have to spend time and money to test) and non-compliant cars (older or not street legal) cannot game the system as the "inspection" can come at any time in nearly any location. This is starting to be put into trial in a few states.

Relevant literature:

Seminymous Coward

This is staggeringly simple to solve: If the car hasn't been driven enough to generate emissions readings, it gets an automatic pass. It's not exactly contributing a lot of emissions. If someone attempts to game the system by driving 149 miles a year (or is it ever?) then that outcome is acceptable.

It's much more of a problem that they trust the OBD computer to tell the truth. Since every car apparently has the equipment to log its own emissions, I can't imagine the equipment to independently verify it would be that expensive. Perhaps the car is computing the emissions from readings on inputs and other outputs combined with some assumptions on the nature of the fuel? If so, that's even sillier.


Had to correct your uninformed guess as to the nature of how OBD works - emissions are calculated (from dozens of sensor measurements and run through complex models) with very good accuracy and compared against out-of limit tolerances. This, combined with a diagnostic of the 'health' (e.g. failed temp sensor) of the emissions sub-system combines to produce a 'pass' or 'fail' (generally accompanied by a 'check engine' light).

Put it this way - (if you know about cars in general) full electronic control of variable timing/injection, drive by wire, and the actual emissions controls (EGR, diesel particulate filters, multiple injections/stroke) takes millions of lines of code, goes through years of testing, and must be verified to perform within fine limitations by the EPA. The readings are correct. (ie. calculating nox output is a hell of a lot more simple relative to the extreme complexity behind simply running the engine in modern vehicles). This is all, by the way, transparent to the driver - which in and of itself is a monumental feat of engineering (which ironically leads to the general public not knowing much on the topic).

This doesn't mean the system can't be defeated in various ways (sensor spoofing, etc.), but that's a different issue, and is continually countered by more sofisticated anti-tampering/tamper-detection methods - likely to be an endless battle but at least relegated to a small minority of the driving population).

FYI - the reason it needs to build up a history (generally miles driven +/- engine idle time +/- engine under load time) is that emissions can vary greatly based upon numerous conditions, and it takes time to have statistical confidence.

IMO, as an aside, I'm having difficulty simpathizing with her - if she drives so seldom, obviously has alternative modes of transportation, and all but admits she doesn't care to drive anymore (apart from the occasional freedom to do so), the ownership cost of a car for her doesn't make much sense to me - and in this case, $15 worth of gas is just the price she has to pay for owning a car she rarely uses, relative to the overall environmental benefit.

(Worked on OBD in the automotive industry for many years).


Sam G

In many states, a solution (of some sort, for some cases) has already been arrived at:
In Maryland, vehicles driven less than 5,000 miles per year, and owned by those over 70 years old are exempt from emissions regulations. Similar exemptions are in place in many states across the country. An expansion of this exemption - or some similar mileage-based alternative testing method - could be used to solve this problem.

Skip Montanaro

That the emissions data aren't saved in flash memory or some other memory/storage technology which doesn't require constant refresh is amazing.


The real fix might be If you are not using your car, rent it out to others who need it and make enough money to pay down the loan.


If they exempted cars with dead batteries, people with polluting cars would just disconnect their batteries.


Missouri has tried and moved away from both actual testing of emissions and remote sensing. Only the more urban areas of the state are covered.

I have lived in the St. Louis area for more than 25 years. It started out capturing all the emissions and measuring at local stations.

Then we converted to a blessed company with dedicated facilities. For older vehicles they attempted to simulate a particular driving profile by putting your car on a treadmill and measuring. These folks also had vans that they would park on the shoulders of freeway entrance ramps. Even if you passed this way you had to send them money or the certificate was not validated.

Now we are back to local stations where they just hook up a computer. It is possible that any vehicle without an OBD is exempted but I am not sure.

Last year I bought a used car in a part of the state that has not emissions check with the provision that it pass the safety inspection. When I brought it home and tried to get an emissions check the technician failed it because a previous owner has removed one of two catalytic converters. I was covered because one of the safety inspection checks is that all of the original equipment converters have to still be there or replaced.



I think the problem is not with the emissions testing program (however much that could be improved), it's with Mr. Kim's decision to keep a car that he rarely uses. Far better to sell it to someone who can make use of it. Saving the cost of annual registration, emissions tests, and insurance should be enough to cover renting a car for the few occasions he needs one.


How big is the potential pollution problem from modern automobiles anyway? Is it greater than the pollution released by driving all cars to the emissions testing center every two years or so? I'd like to see the numbers that justify the program.

In Ohio E-Check counties, cars more than 25 years old are exempt -- and we know they're all clean.

Didn't we get rid of all the dirty old polluters with the Cash for Clunkers program?

Joe Dokes

The reason that you need to drive the car, is the fact that you can buy a code reader for around fifty dollars. This tool allows you to diagnose many problems with your computer controlled vehicle. It also allows you to "clear" the codes in the car. Thus, if you had a problem you could simply hook up the diagnostic computer, clear the codes and pass the examination.

Requiring you to drive a certain distance keeps you from cheating.

The cure for your problem is called a battery tender, also known as a float charger. This is a small battery charger that will keep your car's batter topped off, so your factor computer won't reset.


Joe Dokes