LONDON/SAN FRANCISCO (Reuters) – Uber drivers in London and major U.S. cities held a series of strikes on Wednesday to protest the disparity between gig-economy conditions and the sums that investors are likely to make in Friday’s blockbuster stock market debut.

Protests were sparsely attended in London, New York and California, and rides appeared easily available in some cities where strikes were called.

Drivers and regulators around the world have long criticized the business tactics of Uber Technologies Inc. The expected valuation of up to $90 billion in its initial public offering on Friday is proving to be the latest flashpoint.

Unions in Britain said support for the strike was strong, with drivers staying at home and passengers using the #UberShutDown hashtag to pledge solidarity