creating shopping and residential areas for middle- and upper-income residents. López Obrador used fiscal policy to encourage private sector investment in housing. He granted construction firms tax breaks and liberalized zoning regulations, leading to the construction of more condominiums and office buildings during his tenure than during any other period in Mexico City's history. New high-density condos emerged in the upscale neighborhoods of Polanco and Lomas de Chapultepec. To improve traffic flow on the city's two main inner-city roads, Periférico and Viaducto, he added sections of second stories to the Anillo Periférico and renovated about 10% of those roads. The Metrobús, an express bus service based on the Curitiba model, was built down Avenida Insurgentes, cutting through the city some 20 km from north to south. Response to Tláhuac lynching López Obrador's popularity diminished after the lynching of two federal law-enforcement officers performing an undercover investigation in Tláhuac in November 2004. The Mexico City Police rescued one agent, but the city's chief of police, Marcelo Ebrard, and federal Secretary of Public Safety, Ramón Martín Huerta, were both accused of not organizing a timely rescue effort. López Obrador's secretary of government, Alejandro Encinas, was criticized for declaring that the lynching should be understood as stemming from indigenous customary law (usos y costumbres). After a thorough investigation, López Obrador gave Ebrard a vote of confidence, despite a request from President Vicente Fox Quesada for him to be relieved of duty. Later, using his constitutional powers, Fox fired Ebrard, while Martín Huerta, a member of Fox's cabinet, received a reprimand and continued to hold office as Secretary of Public Safety until his death in a helicopter accident. López Obrador later appointed Ebrard as Secretary of Social Development and supported his candidacy in the PRD primaries to run for office as Head of Government of the Federal District in 2006. Removal of his immunity from prosecution Elected government officials in Mexico have an official immunity called fuero that prevents criminal charges from being brought against them, which can be removed through desafuero. In 2004 the Attorney General's Office asked Congress to strip López Obrador of his immunity under charges of a misdemeanor (ignoring a court order). The misdemeanor against López Obrador was his refusal to order the cessation of the construction of a private hospital on land expropriated by Rosario Robles (who preceded López Obrador as Head of Government of the Federal District under