Traffic seldom sleeps in Calcutta but several of the newer flyovers leading to the airport are put to bed between 10pm and midnight, catching motorists by surprise and occasionally creating a bottleneck.

The police strategy of using guardrails to block flyovers, most of them along the way to the airport from the EM Bypass, has not only stumped motorists but also raised questions about the rationale behind limiting the use of infrastructure meant to ease rather than block out traffic.

On the airport route, the sight of shut flyovers has been known to make flyers nervous. “I was on my way to catch a late-night flight recently when I ran into a snarl caused by a trailer truck breaking down on the narrowest stretch of VIP Road under the Kestopur-Baguiati flyover. Precious minutes were lost before a police team arrived and directed cars to a service road that took us to Baguiati through a route my driver was unfamiliar with,” a businessman recounted.

The absence of proper signage warning motorists beforehand about a flyover being closed is another peeve point. Metro took a drive past three flyovers on Monday night to find out how keeping them shut past 10pm affects traffic.

Chingrighata flyover

Age: 14 years

How much it cost to build: Rs 9.03 crore

What we saw: Two traffic constables at the base of the flyover pushing blue-and-white guardrails to the middle of the carriageway as soon as the clock struck midnight. Asked how cars were supposed to reach Salt Lake or the airport if the flyover was closed, the cops directed us to Broadway, which cuts through Salt Lake from the SAI-Bypass intersection 1.8km away.

Ultadanga flyover

Age: Seven years

How much it cost to build: Rs 70 crore. Another Rs 14.29 crore was spent on repairs after a 123ft long deck slab weighing 156 tonnes collapsed during an accident on the flyover on March 3, 2013. The flyover reopened after a year.

What we saw: A guardrail bearing two signs — “Men at Work” and “Go Slow” — was placed near a cutout of chief minister Mamata Banerjee. A tattered signboard that read “Flyover closed for all vehicles. 23:00 to 6:00hrs” stood on the barricades across the flank a few feet behind the first guardrail. A taxi screeched to a halt and driver Ramesh Yadav, 29, emerged from the car scratching his head.

“Humko pata hi nehi tha ki yeh raat ko bandh rehta hai. Kisi tarah rokey hain (I did not know that this flyover is shut at night. I braked at the last moment),” Ramesh said.

Kestopur-Baguiati flyover

Age: Three years. It was commissioned in 2012 and opened to traffic in 2015.

How much it cost to build: Rs 280 crore

What we saw: Three guardrails were placed next to each other with boards that read “Go Slow”. A lone triangular road sign also had “Go Slow” written on it. Together, they blocked both the airport and the Ultadanga-bound flanks of the flyover. There was no sign explaining why and for what duration the flyover would be shut.

We didn’t see any police personnel.

Kestopur- Baguiati flyover at 12.17am. Gautam Bose

Ultadanga flyover at 12.28am Gautam Bose

The Telegraph