Ch 6-10 Flashcards
Effective range of a siren
limited to 80 ft at a 90-degree intersection
Ambient Noise
- noise in the passenger compartment
- amount depends on speed, radio volume, A/C, and any other noise
- 6-10db above will ensure 100% detectability
- 15db recommended to ensure rapid response from the listener
- on avg, incr. of 1.2db for every 6.2 mph incr.
- ambient noise in idling vehicle = 32.4-66.7db
- traveling at 55mph = 53.4-76.3 db
- effective range can be no more than 80 ft
Attenuation
- process of keeping noise out
- structure of vehicle will reduce sound pressure level of siren approx. 35db
Sound Frequency of Siren
- louder at some frequencies than others
- low frequencies are better able to penetrate body of civilian car
- on avg, sirens produce a max of 124db 10 ft in front of speaker
- Inverse square Law = every time distance doubles, decrease of 6db
- effective range at a 90-degree intersection was limited to 26-39 feet
Effective range of a siren can be no more than ___ ft
80
Windows up or down
- windows can incr. 10-15db
- while stopped, can decrease attenuation approx. 10db
Localization
- once heard, civilian must figure out where it’s coming from
- when sound strikes body of vehicle, it blocks and redistributes over the surface, making it difficult to localize
- in urban environment, sound will reflect off of buildings, also blocking line of sight
- study:
1. in an open room control grp could pick out 45% angle of siren 91% of the time
2. seated in car, fell to 37.6% w/ window open,
26% with window closed
3. CONCLUDED: not practicable for civilian driver to ID the location of approaching siren
Civilian response to a siren
- response of an approaching emergency vehicle to civilian is a complex process including, hearing the siren, localizing, and then reacting
- closing the distance too quickly doesn’t give the civilian enough time to react, will result in crash or failure to yield all together
One of the earliest known uses of sound as a warning device
- found in the Bible, people affected by leprosy were made to warn others of their approach
-Eldred and Sharp “Are present horns, whistles and sirens necessary for communications?”
Negative right-of-way intersections
where the fire apparatus faces a red light, stop sign, or other traffic control device which indications not having the right-of-way
Notice of Approach
- amount of time and distance required for the civilian
- Emergency vehicle doesn’t have right-of-way until a civ vehicle receives the approach, reacts, and GRANTS right-of-way
NFPA 1500
-requires complete stop under the following circumstances:
1. when directed by DLE
2. red lights
3. stop signs
4. neg. right-of-way intersections
5. blind intersections
6. when drive can’t account for all lanes
7. other hazard present
8. stopped school bus w/ flashing warning lights
- requires FFs to wear helmets when riding in open cab or open tiller seat, but no helmet in closed cabs
- as well as hearing pro when cabin exceeds 90db
Account for all lanes of traffic
- see and clear all lanes of traffic before continuing
- if driver can’t see because of obstruction, wait for it to clear or for light to turn green (addresses in NFPA 1500)
Caravanning
- when multiple emergency vehicles drive directly behind each other
- leave plenty of space
- may be blinded by emergency lights in front of them (use dimmers if possible)
- be cautious of civilian drives not accounting for multiple vehicles
Cautions at Green Lights
- steady greens can also be dangerous
- take foot of accelerator and cover break pedal while scanning for hazards
- be weary when no vehicles are stopped at the red, acting as a natural barrier from distracted drivers
Apparatus Vs Apparatus
- be aware of other trucks response routes
- attempt to contract via radio
Rolling an intersection
- may result in serious crash, especially when there’s limited sight distance
- full stop allows time to look both ways and evaluate
- “Keep in mind, our job is to save lives, not trade lives. Not running reds and stop signs, you’re giving yourself permission to act as judge, jury and sometimes executioner for other innocent lives on the road”
Traffic Preemption Devices
- ability to take intersection while approaching, also controls pedestrian signals
- benefits:
1. reduce response times
2. reduce # of emergency vehicle crashes - Disadvantages:
1. won’t resolve conflict w/ other emergency vehicles at the intersection (some will flood lights will flash to notify that another vehicle has captured or is attempting to)
2. interoperability
3. understanding how much time it will take to capture and change
Light-Emitting Traffic Preemption
- strobe light mounted on vehicle, activated by detector head on traffic signal
- large flood light on traffic cross bar activated to notify that intersection is captured
- avg range = 2500 ft
-Limitations:
1. dirty emitter or receiver heads can reduce effectiveness
2. heads can be struck by object and knocked out of allignment
3. line of sight obstructions (trees, lrg vehicles)
4. fog, smoke, inclement weather
Infrared-Activated Traffic Preemption
- uses infrared transmitter
- more discreet and often used on unmarked police cars
- avg range = 1500ft
Sound-Activated Traffic Preemption
- directional microphone mounted on traffic signal arm
- Disadvantages:
1. tripping unintentionally due to loud horns or other sirens in the area
2. misread due to siren reflection
Radio-Activated Traffic Preemption
- activated by radio transmitter
- Advantages:
1. not affected by line of sight, visual
obstruction, or weather
2. capable of warning other emergency vehicles of possible intersection conflict - Disadvantaged:
1. possibility of interference from other devices that use the same radio frequency
NFPA 1451 (7.2.3)
requires initial training and annual retraining on traffic preemption systems
Removing SCBAs from the cab
advantages
- helps ensure seatbelt use
- the extra moments it takes the crew to make up allows the Officer a few extra seconds to size-up the situation allowing for incr in situational awareness
- reduced injuries due to the bulk and weight making it more difficult to exit cab safely
- seatbelt worn correctly, not loose to donn SCBA
Rollovers and Seatbelts (statistics)
According to US Fire Administration’s “Emergency Vehicle Safety Initiative”
- 3/4 people who are ejected will die
1. 8/10 fatalities in rollovers involve ejection
2. 22 times more likely to be ejected in rollover when not wearing seatbelt
3. 80% of FFs killed in crashes weren’t wearing seatbelts
4. Only 3% of crashes in the US are rollovers, yet, are 1/3 of all occupant fatalities (over 10,000 people each year)
Delta-V
- the change in vehicles velocity over a period of time
- gauges severity of non-rollover crash
- manufacturers reduce severity by increasing the time it takes for the crash to stabilize by installing crumple zones and airbags.
- seatbelts will ensure that occupant is properly positioned to allow airbags and supplemental retaints to do their job
Lap belts can cause…
head, spinal, and abdominal injuries as the FFs body is flung against lap belt
