Before revision:  However, unpredictable weather can make real-world testing in adverse conditions  an expensive and time consuming task requiring access to specialist facilities , and weatherproofing of sensitive electronics.
After revision:  However, development of robust autonomous vehicle subsystems requires repeatable, controlled testing - while real weather is unpredictable and cannot be scheduled. Real-world testing in adverse conditions an expensive and time consuming task requiring access to specialist facilities , and weatherproofing of sensitive electronics.