Heavy Acceleration

Heavy Acceleration (重加速), often referred to by the public as Heaviness (どんより), is a special ability of Roidmudes which creates a temporal field that distorts time for everything and everyone in it. It is represented as a red energy field radiating from the Roidmudes, affecting everyone within the set area. People affected by Heaviness still have awareness of the situation due to the fact that the only part of the human body that is resistant to the distortions is the brain, thanks to the fact that Roidmude bodies are made up of a similar material to the cerebral cortex. As such, people can experience the odd sensation of passing out slowly.

As long as one possesses a Shift Car or a Signal Bike, they are able to ignore the time distortions a Roidmude emits when active, unless multiple time distortion effects occur. Anyone who has a resistance to the Slowdown also transfers that resistance to anything they touch.

As shown during the Crash Roidmude incident, some Roidmudes can involuntarily deactivate their time distortion effects when sufficiently damaged, which can be seen as a white dome retreating back into the Roidmude's body. During this time, Mr. Belt had warned Shinnosuke that even Drive can cause Heavy Accelerations.

If the Roidmudes decide to grant a human's desires, they can place a plate resembling a SB memory card on the host's body, which ensures that the host is unaffected by the time distortion effects of Heavy Acceleration. These plates can be reproduced as many as the Roidmudes want, but the Roidmude will relieve the plate from the host's possession after granting the host's desires in order to silence them once their evolution into an Advanced Roidmude is perfected.

While the phenomenon is usually adverse to humans, it sometimes has a positive effect, as the distortion is slow enough to prevent a man from falling to his death from a great height.

As seen in the Gunman Roidmude case, there were special band-like devices created from Roidmude 018's body that can cause Heavy Acceleration surges without leaving any particles behind, though these artificial surges have less ground to occupy, with the device in question being quite capable of being overloaded and stop working. The peddling of these devices was soon stopped by Kamen Rider Mach, who incidentally is also able to cause Heavy Acceleration surges, with his energy field being tinted silver.

In episode 21, after Chase receives modifications from Medic, Mashin Chaser can now create an improved version of Heavy Acceleration called Super Heavy Acceleration (超重加速) simply by absorbing energies in his Break Gunner and punching it into the ground to produce a purple wave that can affect a small area in a certain radius. The effect is so much more powerful than the original Heaviness that it manages to slow down Drive Type Wild despite him having Shift Cars used to counter Heavy Accelerations, and the start up also sends Drive airborne into the air. This Super Heavy Acceleration is so strong, most small objects get disintegrated.

So far, Shinnosuke only has two forms capable of countering this new power: Type Dead Heat, albeit the form would suffer from reduced abilities, and Type Formula, which has so much power that it can move a supersonic speeds even in Super Heavy Acceleration while still retaining its strength.

During the crossover with the Ninningers, a Youkai's Terrible Pressure attack is combined with the effects of a Slowdown, creating a similar effect to the own Chase can create. Instead of actually slowing down those affected however, it instead amplifies their responses to fear and makes them unable to move. Shinnosuke and Gou are able to overcome the effects by transforming into Types Formula and Dead Heat respectively, while the Ninningers simply harden their resolve to break through their fear.