Soem comments on both the article, and other comments here: - It's an interesting assessment, but without know the details of how he did the measurement, take

Soem comments on both the article, and other comments here: - It's an interesting assessment, but without know the details of how he did the measurement, take care in interpreting the results. If he was using a smart-phone just lying on s seat of floor, the data are almost certainly (mostly) meaningless. If he was using a professional triaxial accelerometer that was rigidly or semi-rigidly attached to the floor, the data are more representative. - With regards to comments about the data being related to track conditions. Passenger trains have two sets of suspension - the primary suspension between the axles and trucks (bogies for our European/Asian friends) and the secondary suspension between the truck and the passenger car. The secondary suspension is typically very soft for ride-quality purposes and is mostly isolated from the track. The vertical vibration levels measured here are almost entirely a result of the ride-quality decisions made by the manufacturer and agency engineers, and less so about the track condition. - As pointed out by nhf and inferiorhuman, the side-to-side jerkiness (lateral vibfration) is likely related to track condition and is some combination of track alignment problems and wheel hunting (there the wheels on the solid axle bounce sideways back-and-forth between the parallel rails). - Electrifying the line will have no affect on the cabin vibration unless Caltrains elects to purchase entirely new passenger cars with different secondary suspension design goals. If the new electric locomotives are pulling/pushing the same passenger coaches, the vibration will be the same. - From personal experience I can tell you that the TransRapid TR08 (German system, used in China) can gave similar subjective levels of jerkiness when the guideway configuration has a sudden change.