Air travel produces the highest greenhouse gas emissions per passenger-mile, followed by road travel, rail travel, and water travel.

Nitrogen oxides are the primary air pollutant emitted by vehicles, especially diesel vehicles.

Aircraft are the main source of noise pollution from transportation, especially during takeoff and landing.

Road construction and expansion can fragment habitats, disrupting wildlife movement and ecological processes.

Runoff from roads and parking lots, containing pollutants such as oil, grease, and heavy metals, is the primary cause of water pollution from transportation.

Rail transportation is the most energy-efficient mode of transportation, followed by water transportation, road transportation, and air transportation.

Traffic congestion is caused by a combination of factors, including increased vehicle ownership, poor road design, and inadequate public transportation.

Walking has the lowest carbon footprint among all transportation modes, followed by cycling, public transportation, and electric vehicles.

Air pollution from transportation is caused by a combination of vehicle emissions, aircraft emissions, and ship emissions.

Road construction and expansion can cause soil erosion, especially in areas with steep slopes or unstable soils.

The burning of fossil fuels in vehicles, aircraft, and ships is the primary cause of greenhouse gas emissions from transportation.

Road lighting can cause light pollution, especially in rural areas where there is little other light.

Noise pollution from transportation is caused by a combination of vehicle engines, aircraft engines, and ship engines.

Water transportation can cause water pollution through oil spills, bilge water discharge, and sewage discharge from ships.

Road construction is the primary cause of habitat fragmentation from transportation, as it divides natural habitats into smaller and isolated patches.