As one of three types of flatland universal locomotives, the SBB introduced the Ae 3/5 built by the SLM from 1922 onwards. Since the electrical part came from SAAS, it was nicknamed “little Sécheron”. The power came from a twin motor per axle. With only five axles in total, it had a better power-to-weight ratio than its six-axle competitors, but poorer running characteristics at higher speeds.

Since the express trains tended to be pulled by six-axle machines, the Ae 3/5 was primarily used in regional traffic. In the 1960s, nine locomotives were converted for use with car trains. The first retirements due to wear and tear took place in the late 1960s. However, the majority of the locomotives were retired between 1979 and 1983.

With progressive electrification at the SBB, on the basis of tests with the Fb 2/5 the Buchli drive was selected as the preferred drive for express locomotives in the lowlands. The Ae 3/6^I now had the asymmetrical wheel arrangement 2-C-1, since the bogie had to carry the transformer. It could initially be approved for 90 km/h and later for 100 km/h. The last 78 locomotives built after 1925 were designed for use with lightweight express trains at speeds of 110 km/h. With the delivery of the Re 4/4^I, they were increasingly used with passenger and freight trains. In the end, they were mainly used with regional trains until the last ones were finally retired in 1994.

As part of the planned electrification of the entire network after the First World War, the SBB needed a universal locomotive for lines in the flat land. A locomotive with three driven axles, an output of 2,000 hp, a top speed of 90 km/h and a maximum axle load of 20 tonnes was specified. In addition, special scenarios were specified that had to be completed within a certain time. For example, this involved three round trips on the 117 km line between Villeneuve and Brig with a 480-tonne passenger train. These should be able to be completed in a total of 11.5 hours, including a 15-minute stop at the end stations. In response to these requirements, BBC developed the Ae 3/6^I, Oerlikon the Ae 3/6^II and SAAS the Ae 3/5.

Since Oerlikon did not have a tried-and-tested single-axle drive to offer at the time, Switzerland's last faster rod-driven electric locomotive was developed. It was based on the Fb 3/5 No. 11201 developed for the Gotthard Railway and, like these, had two motors that drove three axles via crankshafts, triangular connecting rods and coupling rods. The traction motors each weighed ten tonnes and, with a diameter of 1,800 mm, were the largest ever used in an SBB locomotive.

Since only one transformer was now required and this could not be arranged in the middle for reasons of space, an asymmetrical wheel arrangement was used. At the end of the locomotive where the transformer was located, there was a bogie with lateral play of 80 mm. At the other end there was only a bissel axle, which had a play of at first 83 and later 70 mm. The middle drive axle also had lateral play of 15 mm. Despite the rod drive, this chassis was suited for the specified maximum speed of 90 km/h, which was even increased to 100 km/h in 1929.

After the first 20 vehicles, some weak points became visible, which were remedied in the next 40 vehicles. In the first batch, the transformer proved to be too small compared to the traction motors, so later a more powerful but lighter one was used. The steps of the tap changer in the lower portion were also distributed too roughly, which led to rough starting behavior and led to a different distribution of steps in the later locomotives.

Initially, the production of the locomotives was faster than the area of service grew with progressive electrification. As a result, some locomotives were temporarily classified as surplus, although all express, passenger and freight train traffic between Basel and Lucerne was handled with the Ae 3/6^II. The 60 locomotives were soon spread over a large area in the flatter parts of northern Switzerland, but were increasingly pushed east with the advent of the Ae 4/7. Later they were increasingly used in tasks such as pilot service and were withdrawn between 1965 and 1977. Today only No. 10452 is preserved, which is used every now and then and has the number 10439 written on.

As the Ae 3/5 designed for the newly electrified flat lines of the SBB had insufficient running characteristics in curves, a locomotive called Ae 3/6^III was built in 1925 that was intended to solve this problem. By changing the Bissel axle on one end of the locomotive against a two-axle bogie, both the wheelbase and the guidance in curves were to be improved. Since the Ae 3/5 was called “small Sécheron”, the Ae 3/6^III got the nickname “medium Sécheron”.

The electric part made by Sécheron was virtually identical to that of its predecessor. This means that they had the same 1,365 kW hourly output and the same Westinghouse quill drive. Apart from this, the changes in the chassis didn't bring the desired effect and the top speed was still limited to 90 km/h. Nevertheless, ten more have been built in 1925 and 1926. They were retired between 1968 and 1980 and today, 10264 is being preserved in an operational state by SBB historic.

For the ever heavier passenger and freight trains on the Gotthard after World War II, the SBB needed more powerful electric locomotives. The requirements which resulted in the Ae 6/6 included an hourly output of 6,000 hp, a maximum weight of 120 tonnes and an effective dynamic brake. As basis for the development, SLM, BBC and Oerlikon used the CC 6051 delivered to the SNCF in 1950.

The Ae 6/6 had two three-axle bogies and was designed in a modular system that facilitated repairs. With a top speed of 125 km/h and a starting tractive effort of 392 kN, it was sufficient for all types of trains and could haul 600 tonne trains up the Gotthard with 75 km/h. It didn't have multiple controls, what was deemed unnecessary at this time due to their high power.

With their livery that included chrome lines and the coat of arms of Swiss cantons, the first 25 locomotives earned international popularity. The next 95 were christened after towns, but the founding of the new canton Jura led to an additional one being renamed in 1979. As early of 1969, No. 11414 was modified for high-speed service and was tested in Germany at speeds of more than 200 km/h.

When the four-axle Re 4/4 III and the much more powerful Re 6/6 were introduced on the Gotthard, the Ae 6/6 were sent to flatter regions. In the new scheme, they were soon renamed to Ae 610. Due to their top speed, they were only used in freight traffic since the nineties. After their retirement between 2002 and 2013, 13 have been preserved, of which six are still operational. Others had been earmarked for preservation either by SBB Historic or by private associations, but were not restored or were even scrapped.

To avoid the use of helper locomotives or double heading altogether on the Gotthard, the SBB ordered two prototypes of heavy electric locomotives from the SLM. In order to use them on the whole route without changing the locomotives, they had to have a top speed that was fast enough for passenger trains on the flat sections. Each half of the double locomotives was built with four driving and three carrying axles. They had a device that could increase the adhesive weight by removing weight from the carrying axles. 

The first prototype delivered in 1931 was No. 11801. It had Buchli drive units on one side and technically resembled a double Ae 4/7. 11851 delivered in 1932 had SLM universal drives and somewhat more power. In 1938, a third streamlined locomotive with a powertrain similar to 11851 was built. It got the number 11852 and was called “Landi-Lok” since it had been built to be exhibited at the Swiss National Exhibition. With an hourly output of 5,514, 6,470 and 8,162 kW (7,500, 8,800 and 11,100 hp) they were the most powerful locomotives in the world at this time.

After these three locomotives, no more Ae 8/14 have been built. With the advancements in multiple controls, it was more feasible to use a smaller locomotive on the flat sections and add another one at the beginning of the ramp. After only the first two had been built for the SBB, also the third was bought up by them since there was demand for heavy freight locomotives at that time. After the third was retired due to a fire in 1971, the others remained in service until 1975 and 1976. Today the first one is operational and the third one came to the SBB Historic team at Erstfeld in June 2024 after being on static display in Lucerne.

The Be 4/6 No. 12303 to 12342 were 40 electric express locomotives ordered by the SBB for service on the Gotthard. They were directly based on the Fb 2x2/3 prototype No. 11302 and had already been ordered in 1918 when the prototype had not yet been completed. The requirements included a top speed of 75 km/h and the haulage of 300 tonne trains on the Gotthard ramps with 50 km/h.

The mechanic part was produced by the SLM, while the electric part came from BBC. The locomotives had two bogies with two driving axles and a leading axle each. Each bogie had two traction motors which acted on a common crank axle and powered the driving axles via coupling rods. The first batch of twelve built in 1919 had 1,230 kW and did not have a dynamic brake. Three other batches built in 1920 and 1922 delivered 1,500 kW and had a dynamic brake. The first 27 locomotives could be switched from 15,000 to 7,500 V since the Gotthard line had been operated with the lower voltage while steam locomotives were still in use.

Although they met all requirements and surpassed some of them by a wide margin, they were not popular among the crews due to vertical oscillations. As early as in 1929, all expresses on the Gotthard were taken over by the Ae 4/7. Now, the Be 4/6 was used for regular passenger and freight trains and as helpers on steep grades. Over time, they only got small modifications to meet operational requirements. They were withdrawn between 1965 and 1976.