Bridging the Indus at Sukkur had been on the cards since 1872 and for the next ten years, various designs had been considered including a suspension bridge with cables formed of steel links. Bridging the smaller channel of 180 meters between Sukkur and the island of Bukkur was straightforward, since its rocky bottom provided a solid foundation for masonry piers. However, the wide and deep Rohri channel of 260 meters that was filled with silt, posed a problem for constructing piers. In spite of this, in 1882 it had almost been decided to construct a bridge with spans of 75 meters resting on masonry piers, when a severe flood further deepened the channel to 30 meters.
Sir Alexander Rendel, one of the best civil engineers was asked to submit a design without piers. He already had two major railway bridges to his credit: the Alexandra Bridge and the Empress Bridge, but both consisted of spans supported by masonry piers. He proposed a very unusual design of two anchored cantilevers, each 95 meters long, carrying a suspended span of 60 meters in the middle. In spite of an unusual structure, the design was accepted and a contract awarded for the material. Prior to shipping the steelwork, the contractors had assembled the 50 meters tall cantilevers in their yard in UK, much to the amazement of the spectators. With most of the pre-fabrication undertaken back in Britain, the builders on site were often accused of being little more than ‘Meccano engineers’ but the reality was that “erection was a demanding task that stretched the ingenuity of the engineers and the safety of the workers”.
This was particularly so in the case of this bridge and there were doubts if the designer had actually consulted the engineers sufficiently. All praise to Robertson, the executive engineer of the Bridge Division of the Indus Valley State Railway, and his team as well as the 6000 workers employed, for getting 3,300 tons of the most awkwardly designed steelwork into place within two and a half years. It seemed that Sir Rendel had almost gone out of his way to test the ability of the engineers who had to construct two giant derricks each weighing 240 tons (of 5 tons segments), that extended 70 meters over the water while simultaneously leaning inwards. To attach the horizontal tie girders of 86 tons, laborers had to work at a height of 55 meters and four fell and died during construction. According to the original design, the 60 meters long center span was to be floated out and hoisted up but the idea was impractical as the speed of the current was too high for half the year. Therefore Robertson built a temporary bridge on which the suspended span was erected and put in place.
It was inaugurated in 1889 and named Lansdowne Bridge after the Viceroy. It was the longest rigid girder bridge span in the world but its design was subsequently described as ‘bizarre neither economical in weight of material nor cost of shop work’. Because of the rigid nature of the joints at the end of the members, the bridge suffered high deformation and temperature stresses. Therefore from 1924 onwards, the speed of trains across the bridge was restricted to 8 kph. To replace the bridge, a number of designs were considered before and after Independence and ultimately in 1959, work commenced on a single arc structure with a span of 250 meters that was designed by American consultants. The bridge was constructed only 37 meters downstream from the Landsdown Bridge and was the first bridge in the world to have the railway deck slung on coiled wire ropes. It also had the third-longest railway arch span in the world that was not only functional but also graceful. Interestingly it used the same amount of steel as the Landsdown Bridge but was much stronger and could bear heavier trainloads at greater speed. It was named after President Ayub who inaugurated the bridge in 1962.
Though there was a bridge at Attock and Sukkur, there was no crossing over the Indus in the gap of 800 km that separated the two. A large cantonment at Kohat was being established but it could only be supported from Peshawar and accessed over the Kohat Pass. A crossing existed at Khushalgarh (70 km below Attock) that was served by a bridge of boats that had to be dismantled when the river rose in summer. A railway line was extended from Rawalpindi to Jand and in 1902 a cableway powered by a steam engine was constructed that at its best could transport a narrow gauge wagon with a 1½ ton load. However, as a result of poor maintenance, an anchor gave way in 1903 plunging a wagon into the river, and it was decided to construct a rail/road bridge.
The Indus at Khushalgarh flows through a gorge 30 meters deep and 250 meters wide. The width was too large for a single span but fortunately, a headland jutted out from the eastern bank that was exposed in winter, on which a pier could be constructed to support the structure. The design of a two spanned rail/road bridge was prepared by the same team of Rendel and Robertson who worked on the Landsdown Bridge. The eastern span was an anchor span that rested on a massive masonry pier erected at the extreme end of the headland. From this support, a section was cantilevered out 32 meters and another cantilever of similar length was anchored in a cliff at the western end. Between the noses of the two cantilevers, a span of 80 meters was slung. The finished bridge, therefore, had only two spans—one of 144 meters and a second of 92 meters both resting in the middle on the large masonry pier.
The order of the first consignment of the 2000 tons of prepared steelwork required for the bridge was ready for shipping within three months. The entire order was met within 8½ months which was a remarkable speed of manufacturing the anchorage, cast steel girder bearings and the steel work for spans of a 236 meters double decker rail/road bridge. Compact limestone with good weathering properties for the pier and abutments was brought by rail from Hassan Abdal and the Margalla Hills. The substructure work including the pier and abutments was completed in the winter of 1905-6 and the main bridge was completed within two more years.
From 1883 onwards, in less than 50 years the British has constructed five major road/rail bridges across the mighty Indus including two multi-span bridges resting on piers at Kotri (1900) and Mari Indus (1931). Many of them including the ones constructed across the five rivers of Punjab were subsequently strengthened to take heavier loads at greater speeds without upsetting the schedule of trains. It goes to the credit of the British engineers as well as the Indians that they trained like Ganda Singh and his grandson Naurang Singh (the head draughtsman in the Bridge Department of the NWR who retired in 1945), that even 100 years later, these bridges are still standing and the majority are still serving Pakistan and its railways. But there is a darker side to the development of railways in India—a story of greed and exploitation and callous disregard for the masses travelling in Third Class and a lot else that has been brought on record by historians.