He had suffered leg injuries and grazing and cuts to his face and arms.
Police said the vehicle did not stop. It had sped away and crashed soon afterwards as it headed towards Pakowhai Rd.
A passenger was captured by police, but others in the vehicle fled, and they are thought to have included Richards.
Distinguishable by a Black Power-styled fist tattooed on his left cheek, Richards had not been found by early last night.
He was described as male Maori, 1.7 metres tall and of thin build.
Police were looking for anyone who was in the wagon, to which Richards had "connections", said Detective Sergeant Jason Crowe, of Hawke's Bay CIB.
While police have the vehicle, they were last night unaware of any specific other vehicle to which Richards may have had access.
Mr Crowe said: "This was a terrifying experience for the constable who was merely going about his normal duties, trying to keep our roads safe."
Police said Richards already had two warrants out for his arrest, while, according to Hawke's Bay Today files, he has been a regular in courts for more than a decade.
He amassed over 30 convictions before his 18th birthday, on which he was serving 10 months of jail sentences, including four months for snatching a 91-year-old victim's handbag at the Taradale Shopping Centre.
In 2010, just three weeks out of jail following further offences, he robbed the ANZ bank in Marewa.
Though he did not carry a firearm, he passed a note to a teller which stated: "I'll shoot. I'll shoot."
When searched at a nearby cordon, a bag he carried in the robbery was found to contain a hammer.
He was later sentenced to three years and four months' jail.