Following the free-market analogy (for better or for worse), there needs to be an options market, where drivers can lock-in a price for the year, say $5 for that ($2 to $30) route. That way commuters can make better planning decisions. Then during periods when drivers don't exercise their right to take the express lane toll, Transurban (or the option-holders) can sell off their unused passes on-site.

As it stands now all of the volatility in transit times is externalized to the commuter.