Mr Dixon's silver Nissan Almera was pulled over in a lay-by
Police investigating Britain's biggest cash robbery have issued a fresh appeal a week after the £53m raid in Kent.
Photos were released of cars similar to those involved in the kidnap of Securitas depot manager Colin Dixon and roadside checks are under way.
Detectives are searching a farmhouse in Staplehurst, but have not said whether the search is linked to the inquiry.
Four men are being questioned over the robbery, while a further seven people have been released on bail.
Kent Police said more than 1,300 people had called with information since the gang escaped with £53,116,760 from the depot in Vale Road, Tonbridge, in the early hours of last Wednesday.
The robbery was carried out after Mr Dixon and his wife and young son were kidnapped the night before.
The images recreate the fading light at the time of the kidnapping
£1.3m has since been recovered, along with weapons and a number of vehicles believed to have been used during the abductions and subsequent raid.
However, the white 7.7-tonne Renault Midlum lorry used to transport the robbers' haul is still missing.
Police believe cash cages found dumped at Detling Hill, near Thurnham, were also carried by the lorry.
Assistant Chief Constable Adrian Leppard appealed for more information on Tuesday, asking: "Did you see a white lorry anywhere between Tonbridge and Coldblow Lane, near Thurnham, last Tuesday night or Wednesday morning?
"Did you see the white lorry followed by a car in the Tonbridge area early last Wednesday morning?
"Is there an unfamiliar lorry parked somewhere near you?"
ACC Leppard said he also wanted to hear from anyone who saw the police-style Volvo used to kidnap Mr Dixon on the A249 near Stockbury, or the car which abducted his wife and son from their home in Herne Bay.
The pictures released have been deliberately darkened in the hope of replicating conditions at the time of Mr Dixon's kidnap.