We have a name for that ground strap= suicide.
They put a resistor in those- so that in the unlucky (not unlikely- unlucky) event you cross a mains, you do not kill yourself by forming the other side of the circuit. Again, the purpose of a current limiting resistor in any ESD ground strap or workbench is ALSO there to protect you the user and not create a condition of near certain death.
Edit, Sorry, I realize this answer is harsh. When it comes to safety, I just think we need to hold a high standard.
Yes, per official ESD guidelines and standards you may in fact have a hard grounded surface workbench. Yes, I fully acknowledge that in theory with trains, we are dealing with lower voltage power, but at the same time, we may have tools, soldering irons and so forth typically at 120V AC. I have had an AC soldering iron (actually a desoldering iron from Radioshack) internally fail and short to AC at the tip. I destroyed a the very computer once I am typing this reply on because a USB cable was on the workbench, made contact to a board, and this defective desoldering iron was at mains potential.
For a DIY setup, hard grounding (no resistor and copper wire to a copper ground pipe) some layers of aluminum foil might be semi effective at draining some ESD, but there are just better methods and honestly safer. Proper ESD pads and wiring are a better and safer way to go.
A resistance of sufficient resistance to limit current to less than 0.0005 amps (O.5mA), at the highest voltage that may be encountered.
Nominally, 800,000 ohms (800 Kilohms) are sufficient for voltages of up to 240VAC. The value of 1 Megohms is specified because it is a standard value discrete resistor.
