Vehicular metrics

From Wikipedia the free encyclopedia

There are a broad range of metrics that denote the relative capabilities of various vehicles. Most of them apply to all vehicles while others are type-specific.

Measurement American unit Metric unit Affects General preference Notes
0 to 100 km/h (0 to 60 mph) seconds seconds acceleration lower is better
0 to 100 to 0 mph seconds seconds acceleration & braking lower is better formerly common in British publications
Autonomy miles kilometers comfort, safety, economics, range higher is better Autonomous means self-governing.[1] Many historical projects related to vehicle automation have been automated (made automatic) subject to a heavy reliance on artificial aids in their environment, such as magnetic strips. Autonomous control implies satisfactory performance under significant uncertainties in the environment, and the ability to compensate for system failures without external intervention.[1]
Braking distance feet meters safety shorter is better
Brake specific fuel consumption lb/(hp·h) g/(kW·h) economics, range lower is better
traveled Distance miles kilometers economy higher is better, lower is better for a second hand car
Drag coefficient (ratio) (ratio) economics, top speed, range lower is better for moving into/through a fluid(air/water), higher is better for stopping/redirecting with a fluid
Friction or Friction coefficient lbf or (ratio) N or (ratio) acceleration, braking distance, traction, fuel consumption, tyre wear lower is better on kinetic parts(drivetrain), higher is better on static parts[chassis binds/bolts/clamps/composites/nails/screws/welds, control surfaces(brake pad-to-disc & wheel-to-ground patchs)] improved by lubricated drivetrain, dry and clean road surface/adhesion railway, reducing road slipperiness/skid (automobile)
Frontal cross-section area sq ft m2 economics, top speed, range, cargo capacity lower is better if area is too small, vehicle becomes difficult to use
Fuel economy mpg l/100 km and km/L economics, range greater is better (mpg and km/L), lower is better (L/100 km) must be specified on new vehicles for sale in the US & UK
Maximum g-force(s) g or ft/s2 g or m/s2 acceleration, braking (safety) higher is usually better measures cornering, braking or forward acceleration
Ground pressure psi pascals (sometimes bar) traction lower is better in soft ground, reduces bogging; higher with loose surface has greater impact on off-road vehicles
Lift to drag ratio (ratio) (ratio) economics, range higher is better for aircraft improved by narrow, long wings
Noise dB dB comfort, health, awareness (safety) lower is better Noise from traffic, is considered by the World Health Organization to be one of the worst environmental stressors for humans, second only to air pollution.[2] Elevated workplace or environmental noise can cause hearing impairment, tinnitus, hypertension, ischemic heart disease, annoyance, and sleep disturbance.[3][4] Changes in the immune system and birth defects have been also attributed to noise exposure.[5]

Stress from time spent around elevated noise levels has been linked with increased workplace accident rates and aggression and other anti-social behaviors.[6] The most significant sources are vehicles, aircraft, prolonged exposure to loud music, and industrial noise.[7]

There are approximately 10,000 deaths per year as a result of noise in the European Union.[8][9]

A loss in situational awareness has led to many transportation disasters, including the 2015 Philadelphia train derailment.[10]

Power hp kW acceleration higher is better Refers to maximum power (high torque and speed). The rate at which torque is applied. Also the rate at which work is done. Power = Torque × RPM / 5252. Automobile manufacturers publish power measured at the crankshaft (bhp or brake horsepower). However, it is the power a car can produce at the wheels (wheel horsepower or whp) that matters when it comes to acceleration performance. Wheel horsepower equals brake horsepower minus drivetrain losses, which can be anywhere from about 10% to 25%.[11]
Power-to-weight ratio hp/lb W/kg acceleration higher is better
Propulsive efficiency % % economics, range higher is better For rockets and aircraft, percent of the energy contained in a vehicle's propellant converted into useful energy
Rate of climb feet/min meters/min combat effectiveness, economics higher is better Applies to fighter aircraft who need to intercept or evade other fighters. In civilian aircraft this denotes how quickly they can reach optimal cruising altitude.
Roll center inches mm handling Too many variables to state a general preference.
Rolling resistance or Rolling resistance coefficient lbf or (ratio) N or (ratio) economics, top speed, range, cargo capacity lower is better improved by narrow, high pressure tires with narrow, large radius, steel/titanium alloy wheels on steel/concrete. Best available examples are Railroad steel wheels on steel rails.
Second moment psi (lb·sq ft) kg·m2 handling lower permits quicker turn-in for cars, higher is more stable in straight line. The moment of inertia about a vertical axis of a vehicle
Size feet meters handling, safety lower is better for parking on narrow parking slots, higher is better for lateral Traffic collision
Shift time mSec ms acceleration lower is better for vehicles equipped with automatic transmissions
Specific fuel consumption (thrust) lb/(lbf·h) kg/(kgf·h) or g/(kN·s) economics, range lower is better (for any given speed) in airbreathing jet engines it is improved by using more inert air for propulsion (i.e. lower exhaust velocity), in rockets, higher exhaust velocity
Specific fuel consumption (shaft engine) lb/(hp·h) kg/(kW·h) economics, range lower is better for shaft engines less fuel use for a given output power means higher efficiency
specific impulse seconds seconds or kN·s/kg economics, delta-v/range higher is typically better in airbreathing jet engines it is improved by using more inert air for propulsion (i.e. lower exhaust velocity), in rockets, higher exhaust velocity
Top speed mph km/h Maximum rate of straight line travel higher is better Electronically limited in some cars for safety (mostly due to concerns of tire failure at high speed)

A speed greater than the legal maximum/recommended speed limit can be considered as useless/unsafe.

Torque lbf·ft or lb·ft N·m acceleration higher is better Refers to the overall maximum torque an engine can produce, or the maximum torque an engine can produce at a given RPM. 300 lbf·ft would be like applying 300 pounds of force to the end of 1 foot long wrench, or twisting a 2-inch diameter shaft with 3600 pounds of force!
Turning radius feet meters handling lower is better
Weight, mass or Dry weight lb kg acceleration, braking distance, traction, fuel consumption, tyre wear lower is better for vehicle performance and taxation; larger is usually better for vehicles carrying loads
Weight distribution % % handling, acceleration, traction close to 50:50 (%Front:%Rear) is commonly considered better
Gross axle weight rating lb/axle kg/axle durability, economics larger is better for vehicles carrying loads Ultimately limited by the hardness of the road surface and legal limits intended to limit damage to it

See also[edit]

References[edit]

  1. ^ a b Antsaklis, Panos J.; Passino, Kevin M.; Wang, S.J. (1991). "An Introduction to Autonomous Control Systems" (PDF). IEEE Control Systems Magazine. 11 (4): 5–13. CiteSeerX 10.1.1.840.976. doi:10.1109/37.88585. Archived from the original (PDF) on 16 May 2017. Retrieved 21 January 2019.
  2. ^ Münzel, Thomas; Kröller-Schön, Swenja; Oelze, Matthias; Gori, Tommaso; Schmidt, Frank P.; Steven, Sebastian; Hahad, Omar; Röösli, Martin; Wunderli, Jean-Marc; Daiber, Andreas; Sørensen, Mette (2020). "Adverse Cardiovascular Effects of Traffic Noise with a Focus on Nighttime Noise and the New WHO Noise Guidelines". Annual Review of Public Health. 41: 309–328. doi:10.1146/annurev-publhealth-081519-062400. PMID 31922930.
  3. ^ Münzel T, Schmidt FP, Steven S, Herzog J, Daiber A, Sørensen M (February 2018). "Environmental Noise and the Cardiovascular System". Journal of the American College of Cardiology. 71 (6): 688–697. doi:10.1016/j.jacc.2017.12.015. PMID 29420965.
  4. ^ Kerns E, Masterson EA, Themann CL, Calvert GM (June 2018). "Cardiovascular conditions, hearing difficulty, and occupational noise exposure within US industries and occupations". American Journal of Industrial Medicine. 61 (6): 477–491. doi:10.1002/ajim.22833. PMC 6897488. PMID 29537072.
  5. ^ Passchier-Vermeer W, Passchier WF (March 2000). "Noise exposure and public health". Environmental Health Perspectives. 108 Suppl 1 (Suppl 1): 123–31. doi:10.1289/ehp.00108s1123. JSTOR 3454637. PMC 1637786. PMID 10698728.
  6. ^ Kryter KD (1994). The handbook of hearing and the effects of noise: physiology, psychology, and public health. Boston: Academic Press. ISBN 978-0-12-427455-6.
  7. ^ "10. Noise" (PDF). Natural Resources and the Environment 2006. 2006. pp. 188–189. Archived from the original (PDF) on November 14, 2011.
  8. ^ "Noise in Europe 2014". European Environment Agency.
  9. ^ Godwin R (3 July 2018). "Sonic doom: how noise pollution kills thousands each year". The Guardian – via www.theguardian.com.
  10. ^ Accident Report NTSB/RAR-16/02, PB2016-103218: Derailment of Amtrak Passenger Train 188, Philadelphia, Pennsylvania, May 12, 2015, National Transportation Safety Board (adopted May 17, 2016).
  11. ^ "Drivetrain losses (efficiency)". X-Engineer.org. Retrieved 2019-01-01.

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