• H Point: The theoretical location of the occupant’s hip. This is the pivot point of both the torso and the upper leg. Many dimensions will be relative to this.

  • 

• 5 Point / 6 Point Harness: A seatbelt with 5 or 6 belts in total. It restrains the movement of the occupant more than a 3 Point Seatbelt and is safer

  • 5 Point Harness

    • 

    • 1 & 2: Shoulder Belts

    • 3 & 4: Lab Belts

    • 5: Anti Sub Belt

• 6 Point Harness

  • 

  • Similar setup to 5 Point Harness however Antisub Belt is two separate belts

• Passthroughs: Cutouts in the seat to allow the belts of a 5 or 6 Point Harness to pass through the seat uninterrupted (as shown by the red circles in the image below)

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• Seatback: The portion of the seat which supports the back and shoulders of the occupant

• Headrest: The portion of the seat which supports the head and/or neck of the occupant

  • In race/bucket seats this will be the area above the shoulder belt passthroughs

• Seatpan: The portion of the seat which supports the buttock and upper leg of the occupant

• Bolsters: Protrusions/barriers typically found on the seatback or seatpan of the seat (shown by the red circles in the image below) They keep the occupant centered in the seat during cornering.

  • 

• Undepressed Seat Contour: The shape of the seat cushioning (typically viewed from the side) when no occupant has sat in it

• Depressed Seat Contour: The shape of the seat cushioning (typically viewed from the side) when an occupant is sitting in the seat - causing the cushioning to compress

• ILD/IFD: Acronym for Indentation Load Deflection or Indentation Force Deflection. A test to determine the stiffness of a foam. Manufacturers will typically specify the stiffness of their foam in ILD/IFD

  • In this test a circular flat indenter is pressed against a foam sample of standardized width, length and height. 60 seconds after the indenter has achieved 25% or 50% compression, the force is measured 

  • Higher ILD/IFD values = stiffer foam

  • 25% ILD/IFD is for a 25% compression

  • 50% ILD/IFD is for a 50% compression

  • US measurements are in pound-force

  • European measurements are in newtons

Location of the H Point will depend on the type of occupant sitting in the seat at that time (e.g. 5th Percentile Female vs 75th Percentile Male) 

If you know generally which type of occupant will be sitting in the seat the most, you can use their location of the H Point (e.g. you know a 50th Percentile Male will sit in the seat the most - so use their location of H Point in design)

Note: The location of the H Point as per ASC/WSC is different from what is described in this document. For all ASC/WSC regulations use their location of the H Point. For all guidelines in this document use the H Point location described in this document

[11]

Unfortunately, the source for this data does not include the above measurements for 5th Percentile and 75th Percentile Male and Female

If for some reason this cannot be possible, discuss with relevant stakeholders how this can be accommodated

Width of Headrest: Minimum 127mm on either side of the centreline (measured at 65mm below the top of the headrest)  [10]

• Important that the headrest is wide enough to cover the width of the occupant with a helmet on, otherwise it may be too easy for the occupants head to be off centre with respect to their body

Height of Headrest: At a minimum should be parallel to 60mm below the top of the helmet the occupant is wearing (helmets may add 2 inches - 2.5 inches in additional height to the occupant) [8]

• Diagram below is for conventional passenger car where occupant is not wearing a helmet, but in our case the occupant must wear a helmet when the car is driving - thus imagine the guide on the right (in the image below) is shifted 2.5 inches up to account for the helmet

• This is to help prevent and mitigate whiplash injuries from occurring in a rear impact collision