The more reliable test is emission test on dynamometer.On dynamometer a typical driving (that issued by standard bodies)is "simulated" ,and during the test we capture all exhaust gases .At the end of test we analyse and declare emission as grams of pollutant per "cycle", as per standard.
In each country ,some organizations standardize the "cycle" (the typical driving).Do you want some additional information?
Methods for car emission determination (English is not my mother tongue ! )
1. Direct sampling
2. Comulative method
DIRECT SAMPLING: in this method probe of analyzer placed in exhaust pipe of car, then car is ignited. Car is in IDLE condition and concentration of emission evaluated by analyzer connected to probe.This method is suitable for police, workshops etc.
COMULATIVE METHOD:In this method car is placed on the dynamometer and based on a interested "driving cycle" is ignited and also tyres revolving.Sampling tube is placed in exhaust pipe and gather and accumulate the whole of exhaust gases during all driving cycle.At the end all accumulated exhaust gases sent to analyzer and it report emission as per gram pollutant/Km or gram pol./mile or gram pol./test.
the method for sampling named:Constant Volume Sampling(CVS).
The detail of this method is different in different countries.
In USA :Ref. recommended code practice SAE J1094 a
driving cycle in USA : FTP 72 includes :
0 sec to 505 sec :cold transient stage (cold start simulation)
505 sec to 1372 sec (867 sec): stablized stage
Any further help ?
