economic analysis on urban planning regulation: the second best policy for traffic congestion

与点状CBD模型相比，面状CBD假设导致了新的扭曲，即出现了以前未被认识到的区位外部性。由于CBD的面积随着UGB限制的实施而缩小，对于居民来说，通勤距离将比以前更远，从而增加他们的通勤成本，从而削弱了UGB限制的影响。如果区位外部性的影响小于拥堵外部性的影响，UGB管制仍然是缓解交通拥堵的有效辅助政策，尽管这种管制的效果要小得多。另一方面，如果区位外部性的影响大于拥堵外部性的影响，则UGB管制将完全失效。在这种情况下，政策建议将鼓励城市规划者扩大城市边界，以提高社会福利。这项研究表明，即使在单一中心城市的框架下，UGB的监管也可能是无效的。

Comparing with the model of point CBD, assumption of area CBD leads new distortion, i.e., location externality to be emerged, which is unrecognized previously. Since CBD area shrinks with implementation of UGB restriction, for residents, commuting distance will be further than before so that their commuting cost will be increased, which weakens the effects of UGB restriction. If influence of location externality is less than that of congestion externality, UGB regulation is still an effective second policy to mitigate traffic congestion although the effect of such regulation is much smaller. On the other side, if influence of location externality is greater than that of congestion externality, UGB regulation will be ineffective completely. In such case, policy suggestion will encourage urban planner to expand urban boundary to improve social welfare. This research demonstrates that even in the framework of mono-centric city, it is possible that UGB regulation is ineffective.