question: Why would an ambulance have a reason to have its lights on but barely going the speed limit?
comment: Because there's a patient they don't want to harm in transit. Those bumps and potholes don't get smoother the faster you go in a 14000lb vehicle. Also, emergency vehicles still have to drive with due care. I'm an insurance adjuster and I've had plenty of ambulance companies as insureds.
passages: Many U.S. states allow volunteer fire, EMS and Search and Rescue personnel to place emergency warning lights in their personal vehicles for use when responding to emergencies. The degree of lighting is mandated by law and also by local custom in most areas, and can vary from a single rotating light on the dashboard or roof, to a setup much like modern police cruisers. Some states also allow volunteer use of sirens and air horns to request the right of way.
   The simplest form of lighting is a steadily burning lamp. These may be white lights used on scene to enable emergency workers to see what they are doing, or they may be colored lights that advertise the emergency vehicle's presence. In the latter case, steadily burning lights are often used alongside rotating or flashing lights rather than on their own, though historically some emergency vehicles only displayed steadily burning lights. For example, California Vehicle Code Section 25252 states: “Every authorized emergency vehicle shall be equipped with at least one steady burning red warning lamp visible from at least 1,000 feet to the front of the vehicle”
   The optical and mechanical characteristics of the lights used can have a significant effect on the look of the vehicle and how readily it gains attention in emergencies.
  
  Section::::Optical types.:Steady burning.
   State of New Jersey 211th Legislature: "Nothing contained herein is intended to grant to any member of a volunteer fire company or a volunteer first aid or rescue squad any privileges or exemptions denied to the drivers of other vehicles, and such members displaying emergency warning lights and electronic horns shall drive with due regard for the safety of all persons and shall obey all the traffic laws of this State including R.S.39:4-81, provided, however, that the drivers of non-emergency vehicles upon any highway shall yield the right of way to the vehicle of any member of a volunteer fire company or a volunteer first aid or rescue squad displaying emergency warning lights or an electronic horn in the same manner as is provided for authorized emergency vehicles pursuant to R.S.39:4-92."
   BULLET::::- In Massachusetts, Police vehicles are only permitted to display blue lights to the front of the vehicle, with white lights being optional. Police vehicles may display to the rear at least one red light and/or amber lights. The law is inverse for fire trucks. Fire trucks are only permitted to display red lights to the front of the vehicle, but may display at least one blue and/or amber light to the rear. Ambulances usually follow the same scheme as fire trucks.
   BULLET::::- In Oregon, and some other states, the ‘command’ vehicle at a fire scene may use a green light to identify its location.
  
  BULLET::::- In Tennessee, motorcycles in funeral processions use green lights.
  
  BULLET::::- In Ohio, snowplows used by the Ohio Department of Transportation use a combination of green and amber lights.
  
  BULLET::::- In New York, Connecticut and Indiana, volunteer EMTs use green lights
   In Virginia any member of a fire department, volunteer fire company, or volunteer emergency medical services agency and any police chaplain may equip one vehicle owned by him with no more than two flashing or steady-burning red or red and white combination warning light units of types approved by the Superintendent of the State Police.
  
  Section::::Colors.
   Ohio is one if the few states that allows the use of sirens in conjunction with lights. Volunteer Firemen and EMTs in the state of Ohio may display red flashing lights and use traditional warning sirens in the same way that a traditional fire apparatus would so long as they pass an inspection by the Ohio State Highway Patrol.
   Blue lights & sirens may also be used on vehicles of that belong to private companies or organizations if their role is either life saving or protecting some vital system of society. This includes but not limited to; Medical & public transport, gas & electricity companies and security (specifically, Security Officers in charge of protecting government buildings & ports).
  
  Section::::Usage by country.:Sweden.:Amber.
   BULLET::::- In California, emergency vehicles must display at least one forward-facing steady-burn red light. Some exceptions are occasionally made for individual vehicles.
  
  BULLET::::- In New York, emergency vehicles must only display red lighting to the front and sides of the vehicle, with white lighting being optional. Blue lights are only permitted to be displayed to the rear.
  
  BULLET::::- In Michigan, emergency road service vehicles such as tow trucks are allowed to use red warning lights only when stationary.
   A key disadvantage of relying solely on internal lighting is the number of lights required to achieve true 360 degree visibility, with most lights usually concentrated front and rear. This can limit the application of vehicles for instances such as scene protection.
  
  Section::::Scientific research.
  
  Section::::Scientific research.:Perception.
   BULLET::::- Ministry of Defence bomb disposal, mountain rescue, nuclear emergency or armament support, or special forces responding to a national security emergency
  
  BULLET::::- National Blood Service or Scottish National Blood Transfusion Service vehicles
  
  BULLET::::- HM Coastguard
  
  BULLET::::- Coal Authority for mine rescue
  
  BULLET::::- RNLI lifeboat launching vehicles
  
  BULLET::::- Mountain and Lowland Search & Rescue
  
  BULLET::::- HM Revenue and Customs when investigating serious crime.
   The lamps are then fitted, typically for a Police vehicle they will have an external roof lightbar, blue repeaters and flashing headlamp relays. The siren can also be controlled by the original vehicles horn switch (steering wheel). This is only activated when the '999' or 'Siren' button is depressed on the controller inside the vehicle.
   Police cars, emergency vehicles, and those competing in road rallies are sometimes equipped with an auxiliary lamp, sometimes called an alley light, in a swivel-mounted housing attached to one or both a-pillars, directable by a handle protruding through the pillar into the vehicle.
  
  Section::::Conspicuity, signal and identification lights.
   Blue flashing lights must only be lit at the scene of an emergency, or when the driver considers it desirable to indicate that the journey being undertaken is urgent, and (in terms of the law) convey to other drivers that they should take special care.
   Section::::Usage by country.:Sweden.
  
  Section::::Usage by country.:Sweden.:Blue.
  
  Police vehicles, medical vehicles and fire engines along with other government vehicles such as the Swedish Military Police and the Swedish Customs Service use white and dark ‘Euro blue’ emergency lights. Ordinary traffic are required to make way for these vehicles if the lights are on.
   Section::::Usage by country.:Hong Kong.
  
  Under Hong Kong Law, Chapter 374G of the Road Traffic (Traffic Control) Regulations: Section 46 "Giving way to animals, police vehicles, ambulances, etc.," drivers must yield to vehicles which are sounding siren and/or flashing light bars.
  
  BULLET::::- Red and Blue: Hong Kong Police Force
  
  BULLET::::- Red only: Fire Services Department fire engines
  
  BULLET::::- Blue only: Ambulances, whether operated by Fire Services Department, Auxiliary Medical Services, or Hong Kong St. John Ambulance; Customs and Excise Department, Hong Kong Correctional Services
   BULLET::::- Green emergency lighting is also used by private security agencies securing certain government buildings and establishments where terrorist organizations may also target. However, in the State of Florida, green is allowed for use by all private security vehicles only in combination with amber lights. (Florida state legislation is pending to also allow flashing clear/white lights in combination with amber/green security patrol lights for added visibility.)
  
  BULLET::::- Green and blue emergency lighting is used by some counter-terrorism agencies whilst responding to terrorist incidents, so as to distinguish the specialist agencies from other emergency departments.
   BULLET::::- Green: Green emergency lighting is used by Registered Medical Practitioner, Registered Nurse or Registered Midwife on emergency calls. While it grants no special exemptions, drivers must give way to them.
  
  BULLET::::- Purple (Magenta): Load pilots escorting a load wider than 5m must display purple beacons to alert other road users there is an oversize load they may need to move out of the way for.
   BULLET::::- Respond: To drive to an incident, urgently but safely, whilst displaying lights and/or sirens. Drivers are exempt from the road traffic act with some conditions, however both organisations have policies imposing further restrictions.. The siren can be switched off at the discretion of the driver when it is not needed (for example, when the road ahead is clear of traffic and easily visible) and reactivated at possible traffic hazards.
   BULLET::::- flood lights, which may similarly be mounted on the side, top, or rear of a larger vehicle.
  
  BULLET::::- load lights, which are used by ambulances and other vehicles with cargo doors to light up the area around the cargo doors.
  
  BULLET::::- alley lights, which are typically found mounted on the side of a police car or emergency vehicle's lightbar, for the purpose of illuminating areas to the side of the car, such as into an alley, or a scene at the side of the road.
   Sometimes referred to as purple, magenta lights are primarily used by heavy vehicle enforcement/escort officers of the NSW Roads and Maritime Services, Victorian VicRoads and South Australian Transport Safety Inspectors. They are also used in combination with amber lights by some council rangers and the New South Wales Ministry of Transport. In Western Australia magenta is used by the Department Of Environment and Conservation ‘HAZMAT Response Unit’. Magenta is also used in some Escort Vehicles used whilst escorting large mining equipment to the north of the state.
  
  Section::::Usage by country.:Australia.:White.
   The main colour for emergency service vehicles is overwhelmingly blue, although there is also widespread use of flashing (white) headlights, and many police vehicles have a set of two rear-facing red flashing lights to indicate that the police car is stopped or to indicate caution. The legal definition of an emergency vehicle limits the use of both methods to vehicles used for:
  
  BULLET::::- Fire, ambulance or police purposes (this includes private fire or emergency ambulance services, but not private security)
  
  BULLET::::- Forestry Commission or local authority when fighting fires
   Section::::Optical types.:LED lighting.
  
  LED-based lighting is becoming very popular in the emergency services for several reasons. Light-emitting diodes are small, completely solid state, very power-efficient, long-lasting (as they have no filaments to burn out) and can be seen very easily even at great distances and in sunlight.
   BULLET::::- Green: Ambulances (some privately operated ambulances use green and red lights)
  
  BULLET::::- Yellow/amber: Utility vehicles, Security Company
  
  Section::::Usage by country.:Spain.
  