Tricycles are statically stable, as long as you're on level ground. They're unstable on canted ground, like driveways, cambered roads. Also dynamically unstable

Tricycles are statically stable, as long as you're on level ground. They're unstable on canted ground, like driveways, cambered roads. Also dynamically unstable taking corners. Bycicles are dynamically stable, since they can lean in corners or stay upright on tilted surfaces, as long as you're moving. That's a reason old-fashioned tricycles aren't popular. Your velomobile might be an exception.