Just thought I'd drop in with this

[Crispina]

[caldrail]

I suppose a lot would depend on how the stunt was being presented. Is it a prisoner sent to his doom? Or a genuine stunt to thrill and wow the crowd by a daring athlete? The former requires failure in the most horrible terms possible, the latter requires absolute success. Either would please the crowd in context. And just to add spice, some hungry wolves or big cats roaming below (a venator could polish them off in the following event). But it strikes me that horses are being risked here. Expensive and valuable animals. Also the charioteer is riding a ceremonial chariot which is too heavy for the stunt (actually, a racing chariot, despite being light enough, would not be strong enough). I wonder if the horse would refuse the jump? Of course, it could be morning entertainment and therefore a comedy item :D