British Transport Police saw the bus at the Cleghorn in South Lanarkshire during Operation Galley, which aims to cut down on dangerous driving at crossings.
The incident emerged as rail union Aslef said it has told its drivers to reduce speeds on open level crossings following the recent incidents.
They have been told to reduce speeds over automatic open crossings to 20mph until Network Rail introduced "appropriate obstacle detection technology" and barriers.
Aslef general secretary Keith Norman said: "Network Rail's unwillingness to invest in vital obstacle detection measures at level crossings has led to this decision today.
"By calling on our members to reduce speeds to 20mph over crossing Aslef members can safeguard the health and safety of both train drivers and the travelling public."
Meanwhile, a British Transport Police spokesman said a train would have been approaching at the time of Monday’s incident.
Two other drivers were also seen passing a red light at the same crossing during the day-long operation.
The incident follows the deaths of three elderly people whose car was crushed by a sprinter train at an unmanned level-crossing in Halkirk, Caithness.
It threw the safety of such crossings into the spotlight.
Inspector Stuart Wilson said: "Motorists at crossings across the country were stopped and issued with advice about the proper procedure when using level crossings on the rail network.
"This initiative was extremely well received by members of the public and rail staff and rest assured Operation Galley will be repeated in the coming months.
"It is unfortunate that there are still those who think they can take a risk when approaching a level crossing and in these cases we will prosecute them."
A 56-year-old man will also be the subject of a report to the procurator fiscal for not following the proper procedures at Charleston level crossing in Perthshire.
The police force said some crossings, such as Charleston, for their safety drivers are required to call the signal operators before and after they cross.
More than 20 BTP officers were joined by members of Network Rail's Community Safety team at sites including crossings at Kingsknowe, Whitelaw and Kirknewton in the Lothians, Gatehead in Ayrshire and Cambus and Blackgrange in Clackmannanshire.
Mark Henderson, Network Rail's community safety manager for Scotland, said: "It's disappointing that, despite all the recent publicity, people are still risking lives by ignoring red lights at level crossings.
"While it's worrying that we continue to see such irresponsible, illegal behaviour, it was a good opportunity to speak to drivers and reassure them that level crossings are safe if used correctly."
A notice of intended prosecution is being sent to the registered owners of the vehicles by police.
The owner of the vehicle has to confirm the identity of the driver at the time of any alleged offence.
The drivers could be charged with failing to obey a traffic sign under the Road Traffic Act 1988.
A fine of £60 and three points on the driving licence can be handed out for the offence.
Angus MacKay, his wife Margaret, both 81, from Inverness, died along with Mr MacKay’s brother Donald, 66, from Latheron, Caithness when a train travelling from Inverness to Wick collided with the car in which they were travelling earlier this month.
The Rail Accident Investigation Branch has launched an inquiry into how the triple tragedy happened, which will also examine wider safety issues over automatic crossings. A Network Rail spokesman said: "Network Rail is willing to talk to Aslef, but the union cannot take unilateral action on this issue and we urge them not to do so.
"Line speeds over level crossings are dictated by a range of factors, including sight lines and traffic flow and are regularly risk-assessed.
"All level crossings are safe if used correctly. However, we have serious concern that Aslef's call to action could have an adverse effect on the safety at open crossings."
Why are you making commenting on The Herald only available to subscribers?
It should have been a safe space for informed debate, somewhere for readers to discuss issues around the biggest stories of the day, but all too often the below the line comments on most websites have become bogged down by off-topic discussions and abuse.
heraldscotland.com is tackling this problem by allowing only subscribers to comment.
We are doing this to improve the experience for our loyal readers and we believe it will reduce the ability of trolls and troublemakers, who occasionally find their way onto our site, to abuse our journalists and readers. We also hope it will help the comments section fulfil its promise as a part of Scotland's conversation with itself.
We are lucky at The Herald. We are read by an informed, educated readership who can add their knowledge and insights to our stories.
That is invaluable.
We are making the subscriber-only change to support our valued readers, who tell us they don't want the site cluttered up with irrelevant comments, untruths and abuse.
In the past, the journalist’s job was to collect and distribute information to the audience. Technology means that readers can shape a discussion. We look forward to hearing from you on heraldscotland.com
Comments & Moderation
Readers’ comments: You are personally liable for the content of any comments you upload to this website, so please act responsibly. We do not pre-moderate or monitor readers’ comments appearing on our websites, but we do post-moderate in response to complaints we receive or otherwise when a potential problem comes to our attention. You can make a complaint by using the ‘report this post’ link . We may then apply our discretion under the user terms to amend or delete comments.
Post moderation is undertaken full-time 9am-6pm on weekdays, and on a part-time basis outwith those hours.
Read the rules hereComments are closed on this article