Vehicle Clearances

1
Vehicle Clearances

• A Ten-Minute Training Topics Presentation

2
Statistics

• Collisions with fixed objects are the second most
  common type of vehicle crashes.
• Hitting a guardrail, abutment or other stationary
  object has led to more than 11,000 deaths and
  more than 500,000 injuries during the most recent
  years statistics per the National Safety Council.

3
Introduction

• When operating any motorized vehicle, we need to
  pay careful attention to the clearance space
  around the vehicle.

4
Introduction

• This includes all dimensions above, below and
  beside the vehicle.
• Its possible to hit tree limbs, bridges, tunnel
  entrances, sideswipe parked vehicles and even to
  get stuck on railroad tracks depending on our
  vehicles design and conditions.

5
Introduction

• Key contributors to these crashes include
• driving while distracted (failing to notice the
  hazard because of electronic distractions,
  fatigue/drowsiness, or other impairment such as
  being ill or influenced by OTC medications, etc.)
  and/or
• assuming theres adequate clearance when there
  really isnt (being unfamiliar with the
  equipment, route, or specific hazard).

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Too Tall?

• If our vehicle is too tall to fit under a bridge
  or go through a tunnel, we could have a
  collision.

7
Too Tall?

• This is especially true along the shoulders where
  curved tunnel entrances or overpasses may be
  closer to the ground than in the middle of the
  main roadway lane(s).

8
Too Tall?

• This is especially common in the Northeastern
  part of the USA and in older cities where large
  roads were not designed for modern commercial
  vehicles.

9
Too Tall?

• The Federal Highway Administration specifies how
  much clearance is needed and how signs are
  provided warning of overhead obstructions.

10
Too Tall?

• A cushion is supposed to be included in case
  the road is repaved and asphalt raises the road
  surface, but the local engineering team should be
  verifying that
  clearances remain
  adequate.

11
Too Tall?

• Some drivers get into trouble when they rely on
  GPS navigation systems that are out of date, are
  missing critical data, or have bad data on board.
  
• Some systems are designed for personal (i.e. car
  uses) and dont have the needed insights to warn
  of low bridges, etc.

12
Too Tall?

• In addition to low bridges, we need to be alert
  for low hanging wires or even overhead pipes
  (think about roads running through or near
  chemical plants, etc.).
• Standards call for these obstructions to have
  minimum clearances, too.
• Unfortunately, they can sag or become lower as
  road surfaces get taller from multiple re-paving
  efforts or hard packed snow ice.

13
Too Tall?

• As a driver, you have the final responsibility to
  exercise caution and avoid a collision.

14
Too Low?

• If our vehicle rides low to the ground, steep
  humps, dips or speed bumps and curbs can create
  problems.

15
Too Low?

• Similarly, low ground clearance may be an issue
  in flooding situations, or dealing with
  unimproved access roads for construction sites or
  rural roads (i.e. logging roads, park access or
  farm/ranch access roads).

16
Too Low?

• Perhaps the most common problem is found with
  long, low trailers that must cross railroad
  tracks.

17
Too Low?

• In order to provide adequate
  drainage, railroad tracks are often built up on
  gravel and ballast.
• This provides a pronounced hump where the road
  meets the tracks.

18
Too Low?

• Often, this is marked with reminder signs,
  especially where there have been collisions in
  the past.

19
Too Low?

• Low slung trailers that can get stuck on the
  tracks present a hazard in several ways a train
  may arrive and crash into the trailer, or the
  trailer may become unstable causing the load to
  shift.

20
Too Low?

• It is possible for a trailer or vehicle with long
  wheelbase to become stuck where the road dips as
  well (in a U shaped profile).

21
Too Wide?

• If our vehicle (or cargo) is extra wide, we may
  encounter trouble when turning, passing other
  vehicles or transiting areas where brush and
  trees grow close to the road.

22
Too Wide?

• Fortunately, there are standards to maintain
  clear zones behind curb lines of at least
  eighteen inches and as much as forty-six feet for
  high speed roads protected
  by barriers.

23
Too Wide?

• Clear zones help in several ways
• if a load overhangs, theres some wiggle room,
  and
• if a vehicle departs the roadway, theres some
  clearance area before the vehicle would likely
  encounter utility poles, trees and sign posts
  (giving the driver a chance to recover and get
  back onto the proper roadway.)

24
Too Wide?

• Additionally, specialized loads or equipment
  typically require a special route plan that is
  scouted prior to the actual trip to document
  clearances and ensure safety.
• Dealing with these specialized loads is beyond
  the scope of this initial report.

25
Too Wide?

• Another area of concern affecting sideswipes is
  backing up using mirrors that are adjusted
  improperly or may be convex (distorting the
  image).

26
Too Wide?

• Backing with mirrors can lead to assumptions that
  side clearances are adequate when in reality your
  vehicle is closer than you realize.
• Make time to get out and look to avoid a
  collision.

27
Road Sign Design

• Fortunately, there are many standards
  regulations affecting road design signage
• roads are usually engineered to provide standard
  minimum clearances (including shoulder widths),
  and
• signs should be provided whenever there are
  exceptions to these minimums.

28
Road Sign Design

• In some parts of the country, there are cars
  only parkways which feature clearances too small
  for commercial vehicles.
• Periodically, larger vehicles find themselves on
  these parkways as a consequence of poor
  directions, over reliance on GPS systems or
  failing to notice a warning sign.

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Road Sign Design

• If you do accidentally end up on a cars only
  parkway,
• pull over as soon as possible and turn on your
  hazard lights
• then call 9-1-1
  for assistance.

30
Road Sign Design

• Drivers who kept driving (possibly assuming
  theyd find an off ramp) often encountered a low
  overpass before they could exit the road way.

31
Road Sign Design

• If you see a low clearance situation, get out and
  look or find an alternative route.

32
Road Sign Design

• Unfortunately, signs can go missing, maps may not
  get updated and we can encounter situations where
  conditions were recently changed (i.e. a road may
  be repaved by adding a layer of asphalt without
  considering that the clearances have been altered
  by as much as six inches, etc.)

33
Road Sign Design

• Regardless, its the drivers responsibility to
  operate their vehicle in a safe manner by judging
  available (actual) clearances carefully.

34
Summary

• As a driver, its your responsibility to check
  your route for possible clearance issues.
• Know your equipments clearances on all sides
• Plan your route with care and the proper
  tools/data

35
Summary

• Conditions may change over time what had been
  safe may be impassable now
• Whenever in doubt, get out and look dont guess
• Always wear your seat belt to help protect you in
  case of a collision.

36
Summary

• Eliminate distractions while driving so that you
  can pay full attention to the road ahead for
  tight clearances.
• Driving safely is your responsibility eliminate
  distractions and focus on the road ahead

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