Hi,
Having multiple pages with similar or identical content confuses the search engines and the outcomes in SERPs will be undesirable. Here is the deal: No two unique URLs should serve substantially similar or identical content. If it is the case, you should decide the URL that you would like to rank in the search engines, make others point to it via rel=canonical attribute. In general, the page that targets the most search keyword/phrase can be made the canonical URL or the preferred URL.
If I were you, I would have added unique content to the existing pages targeting the main keyword for the page.
For example, if the page talks about, 'used cars', this would become my target term for the page:
abc.com/cars/used-cars.html
I would also go ahead with a thorough keyword research & analysis to find which keywords/phrases are being searched more in your geo-location or target market, add corresponding pages with highly targeted content for each of these keywords/phrases (if not added already).
The key here is, content that is unique, up-to-date, highly relevant and useful to the visitors. Such content would bring in dramatic improvements to your overall SEO ROI and search engines like Google love such content and these pages will be awarded good positions in the SERPs going forward. As you know, high quality content is a natural link magnet.
Here is an action plan, if I were you:
1. Make these pages unique by adding unique content
2. Do a thorough keyword research & analysis to find new content opportunities in your niche
3. Add new pages with unique content based on the outcome of step 2.
4. Update the Sitemap.xml file and submit it to webmaster tools
5. Repeat steps from 2 to 4 once in 6 months based on the results or as and when required.
Those were my two cents my friend. Good Luck.
Best regards,
Devanur Rafi