LONDON -- If you have a hidden disability or illness, traveling on public transport can be extremely challenging, particularly when it comes to finding a seat.

While "Baby on board" badges are used by thousands of people on the London transport network, an equivalent for people with hidden disabilities, conditions and illnesses has been missing.

That could be about to change. Transport for London (TfL) has just announced that it is trialling a blue badge and card that say "Please offer me a seat", so customers who are less able to stand might be given a space to sit when they need one.

The card can be shown discreetly to fellow passengers if people do not wish to publicly state they have a medical condition.

The badge and card are aimed at customers who find it difficult to stand when using public transport.

"We have received correspondence from many customers asking for a product like this, telling us they often struggle to get a seat, or when they do, customers make them feel uncomfortable," read a TfL statement sent to Mashable.

"We carried out research which confirmed people with hidden disabilities and conditions, or those undergoing treatments, can find it difficult to get a seat when they need one -- particularly if their need isn’t obvious."

Earlier this year, throat cancer patient James McNaught designed a "Cancer on board" badge to help people like him get a seat on the Tube, after he struggled to find one because he did not visibly appear unwell.

TfL wants to recruit 1,000 people for the trial, so it can determine whether the badge and card help people get a seat when they need it, and to assess fellow passengers' reactions. According to TfL, if the trial is successful, the badge and card would be made more widely available in 2017.