<select name="destination">
      <optgroup label="N Line">
        <option value="Times">Times Square</option>
        <option value="34">34th</option>
        <option value="28N">28th</option>
        <option value="23N">23rd</option>
        <option value="Union">Union Square</option>
        <option value="8N">8th</option>
      </optgroup>
      <optgroup label="6 Line">
        <option value="Grand" selected="selected">Grand Central</option>
        <option value="33">33rd</option>
        <option value="286">28th</option>
        <option value="236">23rd</option>
        <option value="Union">Union Square</option>
        <option value="Astor">Astor Place</option>
      </optgroup>
        <optgroup label="L Line">
        <option value="8L">8th</option>
        <option value="6">6th</option>
        <option value="Union">Union Square</option>
        <option value="3">3rd</option>
        <option value="1">1st</option>
      </optgroup>
    </select>

And in my main.rb

get '/result' do
    @origin = params[:origin]
    @destination = params[:destination]

    erb :result

end