Locomotives in Indian Railways can indeed achieve higher speeds without the burden of attached coaches. Without the additional weight and drag of passenger or freight cars, a locomotive can accelerate more quickly and reach its top speed more efficiently. For instance, the WAP-5 electric locomotive, which can reach speeds up to 160 km/h, might perform even better when running solo.
However, operational constraints and safety regulations typically limit such high-speed runs to controlled environments like test tracks. In regular service, the primary focus remains on safe and efficient transportation of passengers and goods.