The expected surge of Tesla’s robotaxi service in Texas isn’t happening so far. The number of vehicles on the road pales in comparison to ones under the Waymo and Uber banners. That could be a painful truth for investors who were promised a strong autonomous vehicle push from the automaker. Austin-based Tesla had just 42 registered robotaxis as of the end of May, according to a Texas Department of Motor Vehicles database . The same registry showed 577 vehicles registered to Waymo and 317 to Avride and another 47 to Nuro , both Uber partners in that company’s robotaxi expansion.  A recently enacted Texas law requires AV operators in that state to self-certify that their vehicles comply with Level 4 SAE standards. The rules became enforceable on Thursday.…