vacant houses' tree caused sidewalk to rise 1-4" 78 yr old neighbor's tripped 2x & fallen on face. Electric wheelchair must go into busy street.cannot negotiate sidewalk for fear of tipping over. I have written to 1)Mayor Nutter,2)Fran Burns (Commissioner L^I) 3 letters to Wells Fargo bank, 7 phone calls to Bank of America, visited & called City Councilman O'Neills' office. ALL TO NO AVAIL!!!