natural gas bus;natural gas vehicle;emissions from diesel;diversification of energy source;diesel risk reduction program;international organization for standardization ...  See More + airborne particle;price of natural gas;management of water resource;evaluating water institution;direct investment and trade;economies of scale;diesel bus;transit bus;natural gas reserves;oxides of sulfur;oxide of nitrogen;substitution of diesel;air quality improvement;combustion of diesel;diesel particulate emission;exhaust emission reduction;fuel injection system;gas-to-liquids;oil import bill;amount of gas;compressed natural gas;marginal social cost;adequate health care;central business district;electronic control system;new zealand dollar;combustion of biomass;ambient air quality;natural gas industry;natural gas pipeline;gas distribution pipeline;high tax rate;choice of fuel;net present value;bulk water pricing;urban air pollution;Air Quality Management;price of fuel;educational classroom use;greenhouse gas emission;emissions from sources;natural gas use;diesel emission standard;liquefied natural gas;vehicle fuel economy;industrial country;ambient concentration;conventional diesel;diesel vehicle;vehicle tax;clean diesel;gas cylinder;incremental cost;fuel tank;energy content;secondary particle;particle size;gasoline vehicle;vehicle exhaust;synthetic fuel;light-duty vehicle;urban bus;taxation policy;mass transit;relative price;liquid fuel;light hydrocarbon;fleet operator;end-user price;transit operator;retail price;filling station;administrative arrangement;health effect;transport fuel;octane number;engine technology;bus operator;road traffic;equipment manufacturer;principal source;bus fleet;vehicle maintenance;environmental grounds;social choice;air contaminant;gaseous fuel;fuel cost;black smoke;large vehicle; ;  Natural gas; Bus transportation costs; Buses; Diesel fuels; Air pollution; Vehicle emissions; Emissions control; Bus maintenance & repair; Government role; Fuel taxation  See Less -