Two hard technical problems o In practice it is very hard to: (1)Estimate external marginal delay costs (extensive data analysis or difficult simulation is typically needed) (2)Determine equilibrium congestion tolls (trial- and error approach that may take long time to converge is used sometimes) o Queuing theory has much to offer(especially with regards to the first problem) under certain conditionsTwo hard technical problems · In practice it is very hard to: (1) Estimate external marginal delay costs (extensive data analysis or difficult simulation is typically needed); (2) Determine equilibrium congestion tolls (trial￾and error approach that may take long time to converge is used sometimes). · Queuing theory has much to offer (especially with regards to the first problem) under certain conditions