Why would they want the maintenance headaches with the train sizes ML runs? DMU's were discussed as an option when ML started. And, they were rejected due to maintenance issues with every vehicle requiring a much higher level of maintenance for the train lengths and passenger loadings they expected.

To be fair, the track record on O&M costs for DMU's was particularly dismal back then, lacking in sufficient passenger carrying capacity, and more costly O&M. Today there is some better product out there in terms of capacity, but the O&M cost problem remains.

My view, as it was back then, and is still, that unless you are an electrified system, and have the train and passenger volumes sufficient for EMU's, and require flexibility to add significant cars for larger trains sizes to meet peak demand, you're still better off with locomotive hauled commuter trains. It's just one of those math things.....

A few systems like the North San Diego DMU operate what are essentially glorified "rail busses" of a maximum of one or two car "trains". It was my best professional judgement, based upon the options ML had, that this was the right choice for ML's needs.

And, yes, it has also always been my opinion that this was probably yet another bad decision that SMART made in using more costly DMU's to emulate a kind of poor man's LRT, along with the high platform boarding.

Mark, your answer is wrong, FRA compliant DMU's and regular train consists operate just fine on the same choo-choo tracks Non compliant DMU's are a different matter, which is why systems like North County operate, time separated from the freight services.