International Experience and Best Practices - Clean Air Initiative

APPENDIX B. CASE STUDY OF MEXICO CITY
Air pollution is a chronic problem in Mexico City, one of the largest cities in the world with
20 million people. Ozone levels are often very high, exacerbated by Mexico City’s high
altitude and susceptibility to severe thermal inversions in the winter (having a bowl-like
geography similar to Los Angeles). More than 3 million cars and 30,000 diesel vehicles
are prime culprits in making the city’s air unhealthy.
For more than 15 years, Mexico City has implemented an I/M program. It is not only
among the longest running programs, but it is also regarded as one of the most
successful in the developing world. The primary reason for success is that program has
evolved. It has discarded what didn’t work; it has discovered problems and implemented
solutions. A brief history of Mexico City’s I/M program for cars illustrates this key
attribute.
B.1. I/M for Automobiles: A Brief History
In 1988 Mexico City launched an I/M program for automobiles for vehicles of a certain
age. Initially, the city used publicly-operated test-only centers to conduct the inspections,
but soon authorized test-and-repair centers as well, thus allowing a “hybrid” system to
develop. In 1991 Mexico City authorized privately-operated test centers and, within two
years, 24 were in operation. At the same time, 500 test-and-repair centers had been
licensed and the public test-only centers had been phased out due to lobbying by private
garages.
Problems with the performance of the test-and-repair centers developed quickly. These
centers began competing for business by lowering the price of inspections and giving
false “passes” to drivers. No effective oversight system was in place to detect the
cheating. Soon an estimated 50 percent of vehicles inspected in test-and-repair centers
were getting I/M certificates irrespective of their emissions.
Responding to these widely perceived problems, the government completely overhauled
the I/M program in 1996, eliminating the test-and-repair centers and increasing the
number of test-only centers. A much stronger system of oversight and quality assurance
was also instituted and the number of automobiles failing the test more than doubled.
In 1997 Mexico City moved to loaded (dynamometer based) testing for automobiles
using the acceleration simulation mode. This change led to more accurate, replicable
test results and allowed tighter emission standards. Loaded testing also allowed
policymakers to tackle the “lean and late” method of cheating. In 2000 Mexico City added
NOx standards to the existing CO and HC standards. As noted in Chapter 3, NOx testing
can detect the “lean and late” syndrome and it has proved effective in Mexico City. The
government found, however, that the NOx standard led to such a high failure rate that
additional fine-tuning was needed. Rather than explicitly change the standard, the city
modified the testing protocol to allow more vehicles to pass.
Throughout this period, Mexico City also found that it needed to license additional
test-only centers in an effort to balance public convenience with the profitability of the
centers. Too few centers led to long lines and irate drivers. Too many centers led to fee
87