I am skeptical that vehicle emissions programs like Maryland's VEIP are a net win overall.

  • You generate emissions by driving there in the first place, and idling while you wait your turn.
  • Almost all newer cars will pass.
  • If your car fails for whatever reason, you get a waiver once your repair bills exceed a certain amount ($450 in Maryland) -- thus, many cars that fail may never be fully repaired.

The website claims the program makes a (significant) contribution:

By having your vehicle tested, you're playing an important part in Maryland's successful and ongoing efforts to clean our air and water, creating a healthier Maryland for all of us.

What I'm looking for is a cost-benefit analysis: quantify the emissions reductions from cars that failed and are actually repaired, net of additional emissions from additional driving and idling for the test itself.

  • 1
    I was talking to an air quality engineering professor a few days ago and this question came up. Her opinion, as I understood it, was that in general it's probably not helpful, but that cash incentives to retire old and severely polluting vehicles were very effective. But the tests help identify those vehicles. Would be good to find data. Jul 3, 2017 at 18:06
  • 3
    Why would a rational person (granted that there are irrational people in the world) idle while waiting their turn?
    – jamesqf
    Jul 3, 2017 at 18:19
  • 5
    @jamesqf because it's 100 degrees outside and I want to run the air conditioner
    – DavePhD
    Jul 3, 2017 at 19:54
  • 2
    Also, if you have a serial line, the car needs to move forward frequently. One car pulls in to be tested and all the cars behind move up one space. States like Pennsylvania combine the mechanical and emissions test, avoiding that particular problem. The larger problem though is that as written, this question has no notable claim. It's basically the asker's opinion (which may match the objective truth; it's a reasonable opinion).
    – Brythan
    Jul 3, 2017 at 20:23
  • 4
    In order to answer the question, you can't merely count the number of people caught, but you have to postulate how many would pollute if there were no such law - or do you mean to compare it against other legal systems? In Australian states, the inspection system is decentralised and privatised.
    – Oddthinking
    Jul 4, 2017 at 8:01

1 Answer 1


This is an incredibly complicated topic, and research regarding I/M (Inspection & Maintenance) programs goes back decades. Despite volumes of publications (and entire books) on the topic, there is still no clear answer. This is partly due to each state having different requirements, implementation styles, efficacy of inspections, waiver limits, etc., etc. It is too simplistic to think that we can just take "cost of excess emissions prevented" - "cost of I/M program"

You may be interested to know that the EPA Office of Inspector General is planning to inspect EPA's program of oversight into these state-lead programs.

As to the source you posted, it was an analysis done in the late 80's by an economics professor, and much of the data for costs was based on surveys, and the only benefits calculated were for CO and Hydrocarbon reductions. This limits the analysis, as other sources include benefits of reduced accidents due to faulty equipment, as well as NOx and SOx reductions. We also have a very different view of how to calculate benefits today.

One reasonable way to look at the problem is, "were I/M programs reasonable when they were implemented?" This EPA document from 1976 certainly defends that position.

I wish I could be more helpful, but the reality is that there are armies of people looking into this issue, and there is still no resounding consensus. Cars are no doubt cleaner now than they were decade ago, when these programs began. This is likely due, in part, to I/M programs, but that is a difficult claim to "prove". I think we should support more rigorous cost-benefit analyses, especially studies that include the myriad and tangential benefits that I/M programs provide (continued pressure to make cars cleaner, for one), while admitting their limitations (Better I/M may have been able to prevent Diesel cars from emitting massive amounts of pollution in the US).

I hope that was at least helpful.

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .