A family car today weighs considerably more than its equivalent from decades ago, despite lighter materials being available. The increase comes from several requirements that each add mass and then compound.
Crash protection requires structure
Modern occupant protection depends on a body that absorbs energy in a controlled sequence, with crumple zones deforming while a rigid cell around the occupants does not.
Achieving that demands high-strength steel sections, reinforced pillars, side intrusion beams and mounting points capable of restraining loads that older bodies were never designed for.
Testing regimes have also become more demanding, adding offset, side pole and pedestrian requirements, and each new test tends to add material somewhere in the structure.
Equipment has migrated from optional to standard
Air conditioning, electric windows, multiple airbags, sound insulation, infotainment and driver assistance systems now appear across almost every segment rather than at the top of it.
Individually these items are modest, but they arrive together with wiring, control units, brackets and mounting reinforcement that add more than the components themselves.
Sound insulation is a particularly heavy addition, and expectations of cabin quietness have risen steadily, so the material fitted has grown with them.
Body styles shifted toward larger shapes
Buyers have moved from low saloons and hatchbacks toward taller crossovers and sport utility shapes across most markets.
A taller vehicle needs a longer suspension travel, larger wheels and brakes, more glass and more body panel area, all of which add mass before any equipment is fitted.
Raising the centre of gravity also requires stiffer structures and wider tracks to maintain handling, so the increase is not confined to the parts that grew.
Electrification changed the arithmetic again
Battery packs are heavy, and the pack must be protected by its own structure, which adds further mass on top of the cells themselves.
Greater mass demands larger brakes, stronger suspension components and reinforced mounting points, which is the compounding effect engineers refer to as the mass spiral.
Manufacturers counter with aluminium and composite panels, but those materials are used selectively because cost and repairability constrain how widely they can be applied.
Weight has consequences beyond efficiency
Heavier vehicles consume more energy to accelerate and require longer distances to stop, which affects both fuel or electricity use and stopping performance.
Road wear rises steeply with axle load, and parking structures designed decades ago were specified against a lighter vehicle fleet than the one now using them.
Tyre and brake wear also generate particulate emissions that are unrelated to the powertrain, which is why they persist regardless of what propels the vehicle.