In a similar vein to the earlier question about determining the damage track and effects of damage on an object by the Wreck spell...

Bind and Net are both resisted by the Strength of the target and the ultimate effect is based on how much of their Agility you manage to counter. It's generally described as magical "ropes" wrapping around the victim. But the write-up suggests it can be used to similarly restrict moving parts on a vehicle or drone - but how do you determine the Strength of a rotary motor? What is a vehicle's Agility attribute?

I'd assume the simplest substitution would be to switch Strength with the vehicle's OR as with other effect-an-object modifications. Though because that's mostly a measure of separation from nature, rather than power or complexity of the device, it presents the problem that Binding a palm-sized Kanmushi is as difficult as stopping a helicopter rotor or a tank turret (or, conversely, as easy to do the latter as the former). Though I suppose this is a common problem with the TK spells, in general. Similarly, it's easier (by the rules) to Animate a solid stone statue, rather than an articulated model skeleton.

Taking that aside for a moment, how do you determine effect? Of the three stats related to motion, handling is a direct dice-pool modifier, speed is a benchmark, and acceleration is equivalent to the walking/running modifier. They don't appear to have a stat that easily converts. I suppose you could say that a Bind spell that beat OR would force a Crash test - but it still leaves the problem of determining what extra penalties to apply to it.

Suggestions? How did people handle this in 3rd edition? Or is Bind/Net just one of those spells no one ever bothers to take?

If it was me, I'd just use the vehicle's Body attribute for Strength, on the theory that larger vehicles need to have greater power to move them. For Agility, I'd use Pilot, which is already used in place of Agility elsewhere.

I agree on Agility equating to Pilot. Not sure about the strength thing, though. I like deriving strength from body, but IIRC, in Rigger 3 if arms were added to a vehicle appropriate to the vehicle's size, then by default their strength was Body^2. Now granted, in SR4 that may no longer be an appropriate scale, but you don't want your bind spell incapacitating a tank as easily as it does a troll.

I keep forgetting how much higher vehicle body ratings are in SR4.

Body and Pilot should work fine. Add the "maneuver" or "defense" autosoft, maybe?