Vehicle or Facility

Dominant Components

Comments

Commuter Rail or Light Rail Transit On exclusive right-of-way (at-grade or on aerial structure)

Wheel/rail interaction and guideway amplification

Depends on condition of wheels and rails.

Propulsion system

When accelerating and at higher speeds.

Brakes

When stopping.

Auxiliary equipment

When stopped.

Wheel squeal

On tight curves.

In general

Noise increases with speed and train length.

Light Rail Transit in mixed traffic

Wheel squeal

On tight curves.

Auxiliary equipment

When stopped.

Horns and crossing bells

At grade crossings.

In general

Lower speeds mean less noise than for light rail on exclusive right-of-way.

Commuter Rail or Light Rail Transit in tunnel

Fans

Noise through vent shafts.

Trains in tunnels

Noise through vent shafts.

In general

Noise is not a problem.

Station/Parking Facilities

Automobiles

Patron arrival/departure, especially in early morning.

Buses idling

Patron boarding, bus layover.

Auxiliary systems

At terminal stations and layover facilities.

In general

Site specific, with peak activity periods.

Diesel Buses

Cooling fans

While idling.

Engine casing

While idling.

Diesel exhaust

At low speeds and while accelerating.

Tire/roadway interaction

At moderate and high speeds.

In general

Includes City buses (generally two axle) and over the road coaches (generally three axle).