Hi,
on a single router you could use "show interface" and check the load values. You might want to decrease the default load interval to 30 seconds to get more accurate values. The load value can also be obtained through SNMP.
If you are asking for a method to see the load on remote routers: no, it does not exist.
The main reason is, that IP itself does not allow to gather those informations. Either an IP packet is delivered or not. Even if it is dropped, you do not know why. ICMP messages exist for some drop reasons like TTL expired, but not for CRC errors or overload conditions.
Regards, Martin