Vehicular metrics

Last updated

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.

Contents

MeasurementAmerican unitImperial unitMetric unitAffectsGeneral preferenceNotes
0 to 100 km/h (0 to 60 mph)secondssecondsseconds acceleration lower is better
0 to 100 to 0 mphsecondssecondssecondsacceleration and braking lower is betterformerly common in British publications
Autonomy milesmileskilometers comfort, safety, economics, rangehigher is betterAutonomous 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 feetfeetmeters safety shorter is better
Brake specific fuel consumption lb/(hp·h)lb/(hp·h)g/(kW·h) economics, rangelower is better
traveled Distance milesmileskilometerseconomyhigher rating is better for vehicle longevity; lower elapsed is better for vehicle resale
Drag coefficient (ratio)(ratio)(ratio)economics, top speed, rangelower 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) lbf or (ratio) N or (ratio)acceleration, braking distance, traction, fuel consumption, tyre wearlower 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 and wheel-to-ground patchs)]improved by lubricated drivetrain, dry and clean road surface/adhesion railway, reducing road slipperiness/skid (automobile)
Frontal cross-section areasq ftsq ftm2economics, top speed, range, cargo capacitylower is betterif area is too small, vehicle becomes difficult to use
Fuel economy mpg (US) mpg (imperial)l/100 km and km/Leconomics, rangegreater is better (mpg and km/L), lower is better (L/100 km)must be specified on new vehicles for sale in the US and UK
Maximum g-force(s)g or ft/s2g or ft/s2g or m/s2acceleration, braking (safety)higher is usually bettermeasures cornering, braking or forward acceleration
Ground pressure psi psi pascals (sometimes bar)tractionlower is better in soft ground, reduces bogging; higher with loose surfacehas greater impact on off-road vehicles
Lift to drag ratio (ratio)(ratio)(ratio)economics, rangehigher is better for airfoil/hydrofoil; lower is better for stopping/redirectingimproved by narrow, long wings
Noise/Vibration dBdBdBcomfort, stress, health, awareness (safety), Insurance [2] lower is betterNoise from traffic, is considered by the World Health Organization to be one of the worst environmental stressors for humans, second only to air pollution. [3] Elevated workplace or environmental noise can cause hearing impairment, tinnitus, hypertension, ischemic heart disease, annoyance, and sleep disturbance. [4] [5] Changes in the immune system and birth defects have been also attributed to noise exposure. [6]

Stress from time spent around elevated noise levels has been linked with increased workplace accident rates and aggression and other anti-social behaviors. [7] The most significant sources are vehicles, aircraft, prolonged exposure to loud music, and industrial noise. [8]

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

A loss in situational awareness has led to many transportation disasters, including the 2015 Philadelphia train derailment. [11]

Power hp hp kW accelerationhigher is betterRefers 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%. [12]
Power-to-weight ratio hp/lbhp/lbW/kgaccelerationhigher is better
Propulsive efficiency  % % %economics, rangehigher is betterFor rockets and aircraft, percent of the energy contained in a vehicle's propellant converted into useful energy
Rate of climb feet/minfeet/minmeters/mincombat effectiveness, economicshigher is betterApplies 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 inchesinchesmmhandlingToo many variables to state a general preference.
Rolling resistance or Rolling resistance coefficient lbf or (ratio) lbf or (ratio) N or (ratio)economics, top speed, range, cargo capacitylower is betterimproved 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)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 feetfeetmetershandling, safetylower is better for parking on narrow parking slots, higher is better for lateral Traffic collision
Shift time mSecmsmsaccelerationlower is betterfor vehicles equipped with automatic transmissions
Specific fuel consumption (thrust) lb/(lbf·h)lb/(lbf·h)kg/(kgf·h) or g/(kN·s)economics, rangelower 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)lb/(hp·h)kg/(kW·h)economics, rangelower is betterfor shaft engines less fuel use for a given output power means higher efficiency
specific impulse secondssecondsseconds or kN·s/kgeconomics, delta-v/rangehigher is typically betterin 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 mph km/h Maximum rate of straight line travel higher is betterElectronically 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 lbf·ft or lb·ft N·m acceleration higher is betterRefers 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 feet meters handlinglower is better
Weight, mass or Dry weightlblb, long tons, cwt kgacceleration, braking distance, traction, fuel consumption, road and tyre wearlower is better for road and vehicle performance and taxation; larger is usually better for large goods vehicles carrying loads
Weight distribution  % % %handling, acceleration, traction close to 50:50 (%Front:%Rear) is commonly considered better
Gross axle weight rating lb/axlelb/axlekg/axle durability, economicslower is better for road and vehicle performance and taxation; larger is usually better for large goods vehicles carrying loadsUltimately limited by the hardness of the road surface and legal limits intended to limit damage to it

See also

References

  1. 1 2 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. "Whole-body and hand-arm vibration" . Retrieved 2022-08-09.
  3. 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.
  4. 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.
  5. 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.
  6. Passchier-Vermeer W, Passchier WF (March 2000). "Noise exposure and public health". Environmental Health Perspectives. 108 (Suppl 1): 123–31. doi:10.1289/ehp.00108s1123. JSTOR   3454637. PMC   1637786 . PMID   10698728.
  7. 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.
  8. "10. Noise" (PDF). Natural Resources and the Environment 2006. 2006. pp. 188–189. Archived from the original (PDF) on November 14, 2011.
  9. "Noise in Europe 2014". European Environment Agency.
  10. Godwin R (3 July 2018). "Sonic doom: how noise pollution kills thousands each year". The Guardian via www.theguardian.com.
  11. 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).
  12. "Drivetrain losses (efficiency)". X-Engineer.org. Retrieved 2019-01-01.