The main modes of public transportation are buses, taxis, and trains. However, the buses and taxis are of a very model, which is much less fuel-efficient. This causes the vehicles to burn much more fuel than normal and produce a lot of greenhouse gases into the environment, thereby increasing roadside pollution. Along with that, the modes of transportation in Hong Kong get extremely crowded and overwhelmed during peak hours, which forces many people to drive their own vehicles to work, which further adds to the amount of roadside pollution produced.