How ISP's in ARIN region create automatic prefix-filters?

Hi, as I understand, ARIN whois database does not contain "route" objects, which are used for example in RIPE region for automatic BGP prefix filter generation. How does this work in ARIN region? I know that at least some ISP's operating in ARIN region use their own whois databases(for example rr.level3.net) which mirror content from other RIR databases, but are there other methods how they update their internal databases with records? regards, Martin