But with smaller populations with fewer than 15 individuals, even a low number of deaths could have a significant impact.
Lead researcher Dr Lauren Moore, from NTU, said: "Hedgehogs are declining in the UK and we have found how even a small amount of roadkill – perhaps just one or two individuals a year – could have devastating effects on an already small population.
"In the past, research has assumed that high roadkill rates have a large and negative impact on hedgehog populations and that a small amount does little harm.
"This does not tell us the full picture and in fact populations vary a lot in terms of size, reproductive rates, other causes of death and food availability.
"We need to better support hedgehog populations until there are tried and tested ways to reduce collisions happening in the first place."
Conservationists said bolstering smaller hedgehog populations, providing habitat to support more animals, and helping them move around to increase viability of populations without crossing more roads were important.
Simple actions could help, such as leaving wild areas in gardens to provide food and nesting sites, and creating "hedgehog highways" – gaps in fences and walls – so they can move safely between gardens and link up with other animals to boost populations, they said.
