I could travel you could travel she could travel we could travel you could travel they could travel
V-ing form
I could be travelling you could be travelling she could be travelling we could be travelling you could be travelling they could be travelling
Perfect
I could have travelled you could have travelled she could have travelled we could have travelled you could have travelled they could have travelled
V-ing perfect
I could have been travelling you could have been travelling she could have been travelling we could have been travelling you could have been travelling they could have been travelling
Negation
Simple form
I couldn't travel you couldn't travel she couldn't travel we couldn't travel you couldn't travel they couldn't travel
V-ing form
I couldn't be travelling you couldn't be travelling she couldn't be travelling we couldn't be travelling you couldn't be travelling they couldn't be travelling
Perfect
I couldn't have travelled you couldn't have travelled she couldn't have travelled we couldn't have travelled you couldn't have travelled they couldn't have travelled
V-ing perfect
I couldn't have been travelling you couldn't have been travelling she couldn't have been travelling we couldn't have been travelling you couldn't have been travelling they couldn't have been travelling
Interrogative form
Simple form
could I travel? could you travel? could she travel? could we travel? could you travel? could they travel?
V-ing form
could I be travelling? could you be travelling? could she be travelling? could we be travelling? could you be travelling? could they be travelling?
Perfect
could I have travelled? could you have travelled? could she have travelled? could we have travelled? could you have travelled? could they have travelled?
V-ing perfect
could I have been travelling? could you have been travelling? could she have been travelling? could we have been travelling? could you have been travelling? could they have been travelling?
Interro-negative form
Simple form
couldn't I travel? couldn't you travel? couldn't she travel? couldn't we travel? couldn't you travel? couldn't they travel?
V-ing form
couldn't I be travelling? couldn't you be travelling? couldn't she be travelling? couldn't we be travelling? couldn't you be travelling? couldn't they be travelling?
Perfect
couldn't I have travelled? couldn't you have travelled? couldn't she have travelled? couldn't we have travelled? couldn't you have travelled? couldn't they have travelled?
V-ing perfect
couldn't I have been travelling? couldn't you have been travelling? couldn't she have been travelling? couldn't we have been travelling? couldn't you have been travelling? couldn't they have been travelling?