The ride car features a ramp at the back, allowing wheelchairs or mobility scooters no wider than 630mm to wheel onto a platform.
There is a seat for passengers who can be lifted out of their wheelchair, as well as a second seat for caregivers or family members.
The ride car is attached to the back of a model train and pulled along the miniature railway, through a tunnel and around the perimeter of the Leamington Domain in a scenic five-minute journey.
Cambridge Model Engineering Society member Corban Fray says the new ride car includes people who might have otherwise missed out on riding the miniature trains.
"Our goal is to make riding trains as accessible as possible, and to put a smile on people's faces."
"We don't want anyone missing out."
The Cambridge Model Engineering Society was founded and opened in 2012.
Formerly located in Rotorua, the group moved to Cambridge after its lease ended.
During winter the trains run every first and third Sunday of the month from 10am to 3pm, weather permitting. The group aims to open every Sunday during summer.
The Cambridge Model Engineering Society has four trains, including a steam train.